1. 2 2 2 2 sin 3 cos 4 sin 5 cos 6x x x x− = − 2. sin sin 2 sin 3 0x x x+ + = 3. sin cos 2 cos 4 0x x x + − = 4. 1 cos cos2 cos4 cos8 16 x x x x = 5. 1 cos 4 sin 4 2sin 2 1 cos 4 x x x x − = + 6. sin .cot 5 1 cos9 x x x = 7. 4 3 sin cos cos 2 sin8x x x x= 8. 1 tan 2 2 sinx x+ = 9. 1 2(cos sin ) tan cot 2 cot 1 x x x x x − = + − 10. 2 2 tan cot 3 sin 2 x x x + = + 11. tan cot 2(sin 2 cos 2 )x x x x+ = + 12. 3 3 cos sin sin cosx x x x− = − 13. sin sin 2 sin 3 cos cos 2 cos3x x x x x x+ + = + + 14. 3 2cos cos2 sin 0x x x+ + = 15. 2 (2sin 1)(3cos4 2sin 4) 4cos 3x x x x+ + − + = 16. 6 6 sin cos cos4x x x+ = 17. 8 8 10 10 5 sin cos 2(sin cos ) cos2 4 x x x x x+ = + + 18. 3 cos cos 1 2x x− − + = 19. 3cos cos 2 cos3 1 2sin sin 2x x x x x + − + = 20. 1 1 2 cos sin 2 sin 4x x x + = 21. cos (cos 2sin ) 3sin (sin 2) 1 sin 2 1 x x x x x x + + + = − 22. 4 4 7 sin cos cot( )cot( ) 8 3 6 x x x x π π + = + − 23. 3 3 2 4sin 3cos 3sin sin cos 0x x x x x+ − − = 24. 2 2 2 2 (1 cos ) (1 cos ) 1 sin tan sin tan 4(1 sin ) 2 x x x x x x x − + + + − = + − 25 2 4 2 2sin (4sin 1) cos 2 (7cos 2 3cos 2 4)x x x x x− = + − 26. 4 2 2 4 3cos 4cos sin sin 0x x x x− + = 27. 3 sin ( ) 2 sin 4 x x π − = 28. 2 2 4sin 2 6sin 9 3cos2 0x x x+ − − = 29. 4 4 cos 5sin 1x x− = 30. 2 2 4sin 3tan 1x x+ = 31. 1 2 tan cot 2 2sin 2 sin 2 x x x x + = + 32. sin 3 sin 2 5sinx x x + = 33. sin 3 sin 5 3 5 x x = 34. sin 4 tanx x= 35. cos cos4 cos2 cos3 0x x x x + = 36. 1 1 2sin 3 2cos3 sin cos x x x x − = + 37. 5sin cos2 2cos 0x x x+ + = 38. 5cos cos2 2sin 0x x x− + = 39. 1 ( 1 cos cos )cos 2 sin 4 2 x x x x− + = 40. 2 (sin 2 3 cos2 ) 5 cos(2 ) 6 x x x π + − = − 41. 3 8cos ( ) cos3 3 x x π + = 42. 3 tan cot 2cot 2x x x= + 43. 3 2 4cos 2 6sin 3x x+ = 44. cos cos 2 cos3 1 0x x x+ + + = 45. 2 2 2 sin cos 2 cos 3x x x= + 46. cos3 2cos2 2x x − = 47. 6 6 2 13 cos sin cos 2 8 x x x− = 48. 2 3tan 2 4 tan3 tan 3 tan 2x x x x− = 49. 3 3 2 cos 4sin 3cos sin sin 0x x x x x− − + = 50. 1 3tan 2sin 2x x+ = 51. 3 sin 3 2sin 4cos 3x x x− = − 52. 1 2cos 2 8cos 7 cos x x x − + = 53. 3 sin sin 2 sin3 6cosx x x x+ = 54. tan tan 2 sinx x x − = 55. 4cos 2cos2 cos4 1x x x− − = 56. 3 4cos cos 2 4cos 1 0x x x− − + = 57. cos3 2cos2 cos 0x x x − + = 58. sin 5 1 5sin x x = 59. 1 sin 2 1 sin 2 4cos sin x x x x − + + = 60. 5 7 3 5 1 cos sin (cos sin )sin 2 2 cos sin x x x x x x x + + + = + 61. 6 6 8 8 sin cos 2(sin cos )x x x x+ = + 62. 8 8 1 sin cos cos 4 0 8 x x x+ + = 63. 3 tan 2 sin 2 cot 2 x x x+ = 64. cot tan 2 tan 2x x x= + 65. 3 tan ( ) tan 1 4 x x π − = − 66. 2 2 2 2 3 cos cos 2 cos 3 cos 4 2 x x x x+ + + = 67. 4 4 sin cos 2 3sin cos 1x x x x− = + 68. 2 2(sin cos )cos 3 cos 2x x x x+ = + 69. 4sin 2 3cos2 3(4sin 1)x x x− = − 70. 3 3 cos sin sin 2 sin cosx x x x x+ = + + 71. 4 4 1 cos sin ( ) 4 4 x x π + + = 72. 9sin 6cos 3sin 2 cos2 8x x x x+ − + = 73. tan 3cot 4(sin 3 cos )x x x x− = + 74. 3 sin 4sin cos 0x x x− + = 75. 3 3 cos sin 2cos 2 sin cos x x x x x − = + 76. sin cos 2sin 2cos 2x x x x+ + = 77. 3 3 sin cos 1 tan( ).tan( ) 4 4 x x x x π π + = − + − 78. 3 3 1 cos sin 1 sin 2 2 x x x+ = − 80. 3 2sin cos2 cos 0x x x− + = 81. 3 3 sin cos 2sin 2 sin cosx x x x x+ = + + 82. 3 3 2sin sin 2cos cos cos2x x x x x− = − + 83. 3 2 3 1 cos tan 1 sin x x x − = − 84. 2 3 cos sin cos 0x x x+ + = 85. 3 2 2 3(1 sin ) 3tan tan 8cos ( ) cos 4 2 x x x x x π + − + − − 86. 2sin cot 2sin 2 1x x x + = + 87. 3(cot cos ) 5(tan sin ) 2x x x x− − − = 88. sin 2 2 sin 1 4 x x π + − = ÷ 89. sin 2 4(cos sin ) 4x x x+ − = 90. 2 1 3 sin 2 ( 3 1)cos 1 2 x x + = − + 92. 3 2 3 3sin sin .cos 4cos 0x x x x− + = 93. 1 4sin 6cos cos x x x + = 94. 2 8 10 cos cos2 cos 2sin 1 3 3 x x x x− − = + 95. 2 sin8 cos2 sin 2 2cos 1x x x x+ − = + 96. 4cos 2cos2 cos4 1x x x − − = 97. sin 3 (cos 2sin3 ) cos3 (1 sin 2cos3 ) 0 x x x x x x − + + − = 98. 3 2 2 4cos 3sin cos 3cos 4 4 x x x x− − = 99. sin 3 cos4 4sin 7 cos10 sin17x x x x x+ − = + 100. 2 8cos 4 .cos 2 1 cos3 1 0x x x+ − + = 101. 2 sin sin sin cos 1x x x x+ + − = 113. 2 (cos4 cos2 ) 5 sin 3x x x− = + b. 3 3 4sin cos3 4cos sin 3 3 3 cos 4 3x x x x x+ + = .(HV CNBCVT-2001). d. 2sin 3 x = cosx d. 2 4sin ( ) sin 2 1 6 x x π + + = e. 2 2sin(2 ) 4sin 1 6 x x π + + = a. 2 2 4 3 3 sin x cos x s inx+ = g. 1 1 2 t anx sin x 1+tanx − = + c. 3 2 4 sin x s inx π + = ÷ e. 1 + sin 3 2x + cos 3 2x = 3 4 2 sin x g. 3 4 3 sin x sin x cos x π + = + ÷ h. 1 t anx = 2 2 s inx+ i. sinx + 1 s inx + cosx + 1 cos x = 10 3 a. sin cos 4sin 2 1x x x− + = b. sin 1 cos 1 1x x+ + + = c. sin 2 2 sin 1 4 x x π + − = ÷ . d. 2 sin 3 cos3 sin cosx x x x + − = + . e. 3 3 sin cos sin 2 sin cosx x x x x+ = + + . g. cos sin sin cos 1x x x x+ + = .(ĐH QGHN 97) a. ( ) ( ) t anx+7 t anx + cot x+7 cot x = -14 b. ( ) 2 2 1 tan cot t anx + cotx 1 2 x x+ − = c. 2 2 tan cot t anx + cotx 2x x+ − = ` d. 3 3 2 2 tan cot tan cot 1x x x x+ + + = e. 3 3 1 tan cot 3 sin 2 x x x + + = g. 3 tan 3 cot 4x x+ + + = . a. cos5xcos3 = cosxcos7x b. sin2x - cos5x = cosx - sin6x c. cosx + cos11x = cos6x d. sinx + sin2x + sin3x = cosx + cos2x + cos3x + + + + + =sin sin2 sin3 sin4 sin5 sin6 0x x x x x x =cos cos5 cos2 cos4x x x x e. tanx + tan2x = tan3x g. 2 sinx+sin3x+sin5x tan 3 osx+cos3x+cos5x x c = a. 2 2 2 5 2 3sin x sin x sin x+ = b. 3 3 4 5 2 2 2 2 cos x cos x cos x+ + = c. 8cos 4 x = 1 + cos4x d. sin 4 x + cos 4 x = cos4x 2 sin 2 2sin 1 4 2 2sin cos 2x x sin xcosx cos x x x+ − = + − 79. sin 2 (sin cos ) 2x x x+ = e. 3cos 2 2x - 3sin 2 x + cos 2 x g. sin 3 xcosx - sinxcos 3 x = 2 8 h. ( ) ( ) 1 tan 1 sin 2 1 tanx x x− + = + i. tanx + tan2x = sin3xcosx x 2 osx = 2tan 2 c+ 2 sinx + 3 osx + 3 sinx + 3 osx c c = 2 2 4 2 2 os 9 os 1 os os c x c x c x c x + + − = ÷ ÷ 6 6 sin cos sin 2 1x x x+ + = 3 8 os os3x 3 c x c π + = ÷ (Đặt t = 3 x π + ). 2 2 sin 2 sin sin 2 sin 1 0x x x x+ − + − + = c) 02cossin2sin2)2cos1(cos3 =+++− xxxxx 1. 1 3sin 2 2 tanx x+ = 2. ( ) ( ) 1 t anx 1 sin 2 1 t anxx− + = + 3. ( ) 2 2 t anx.sin 2sin 3 os2x+sinx.cosxx x c− = 4. 6 3cos 4sin 6 3cos 4sin 1 x x x x + + = + + 5. 2 4 tan 5 0 cos x x − + = 6. 2 2 4 2 2 cos cos 3 0 cos 3 cos x x x x + − + − = ÷ 7. ( ) 2 2 2 4 4 tan 10 1 tan tan 0 cos x x x x + + + = 8. 2 cos cos cos sin 1x x x x+ + + = 9. 3 1 3 sin sin 10 2 2 10 2 x x π π − = + ÷ ÷ 10. 2 cos9 2cos 6 2 0 3 x x π + + + = ÷ 2 2 2 2 sin 3 cos 4 sin 5 cos 6x x x x− = − 2 2 21 sin 4 cos 6 sin 10 2 x x x π − = + ÷ 2 3 4 1 2cos 3cos 5 5 x x + = 3 2sin cos 2 cos 0x x x+ + = 2sin cot 2sin 2 1x x x+ = + 2 2 7 sin cos 4 sin 2 4sin 4 2 2 x x x x π − = − − ÷ 1. 3 3 3 cos 4 cos3 .cos sin sin 3x x x x x= + 2. 2 2 1 sin sin sin cos 2cos 2 2 4 2 x x x x x π + − = − ÷ 3. 10 10 6 6 2 2 sin cos sin cos 4 4sin 2 cos 2 x x x x x x + + = + 4. cos cos3 2cos5 0x x x + + = 5. sin 3 sin 5 3 5 x x = 6. ( ) ( ) 2 2sin 1 3cos4 2sin 4 4cos 3x x x+ + − + = 4 4 sin cos cos 2x x x+ = 2008 2009 sin cos 1x x + = ( ) sin 3cos sin3 2x x x+ = + + = + + sin sin2 sin3 cos cos2 cos3x x x x x x + =tan tan2 sin3 cosx x x x 8 8 1 sin 2 cos 2 8 x x+ = 2 8cos 4 cos 2 1 sin3 1 0x x x+ − + = 1. 2 cos 4 3cos 4sin 2 x x x− = 2. 3 3 cos sin 2cos 2 cos sin x x x x x − = + 3. ( ) 2 2 4 cos 3 cos 1 2 3 tan 3tan 0x x x x+ + + + = 4. 2 2 2 2 2sin cos 4 sin cos 4x x x x= + 5. ( ) 2 2 sin cos 2 cot 2x x x+ = + 22. 1 1 sin 2 sin 2cot 2 2sin sin 2 x x x x x + − − = 23. ( ) 2 2cos 2 3sin cos 1 3 sin 3cosx x x x x+ + = + 24. 5 3 sin cos 2 cos 2 4 2 4 2 x x x π π − − − = ÷ ÷ 25. sin 2 cos 2 tan cot cos sin x x x x x x + = − 26. 2 2 sin cos 1 12 x x π − = ÷ 27. 4 4 sin cos 1 1 cot 2 5sin 2 2 8sin 2 x x x x x + = − + = + sin sin2 cos cos2x x x x − − =cos cos3 sin2 sin6 sin4 sin6 0x x x x x x 28. 2 4 4 (2 sin 2 )sin 3 tan 1 cos x x x x − + = 30. 2 1 sin 8cos x x = 31. ( ) 2 2 3 cos 2sin 2 4 1 2cos 1 x x x π − − − ÷ = − 2 2cos 4 6 s 1 3cos2 0 cos x co x x x + + + = 1 cos1 sin2)1cos2(cos1 = − −+− x xxx 2 3 2 3(1 ).cotcosx cosx x− = − − 6 6 2 sin 2 1x cos x cos x+ = − 2 2 4sin 2 6sin 9 3cos2 0 cos x x x x + − − = ( ) 2 cos 2 3 2 2 1 1 1 sin 2 x sinx cos x x + − − = + 2 5 2 3(1 ).tansinx sinx x− = − 8 8 2 17 sin 2 16 x cos x cos x+ = xxxx 2cos34cos26sin32cos4 3 +=+ 3 1 8sinx cosx sinx = + 0sincos2cos2sin =−−− xxxx 82cos2sin3cos3sin9 =+−+ xxxx 3 2 cos 2 0cos x x sinx+ + = 3 3 sin x cos x sinx cosx+ = − 4 4 4 (sin ) 3sin 4 2x cos x x+ + = xxxx sin3cos)cos3(sin3 +=− xxxx 3sin43cos29cos33sin3 3 +=− 3 1 8 sin cosx x cosx = + + − =sin cos2 sin3 0x x x 4cos sin 2 2cos2 1sinx x x x+ − + = 3 2sin cos2 0x x cosx− + = 3 3 sin x cos x sinx cosx− = + ( ) 24sin33cossin8 66 =−+ xxx xxxx cos3sin)sin3(cos3 −=+ xxxx 2 coscossintan −= (1) sinxsin2x + sin3x = 6cos 3 x sin3x + cos3x + 2cosx = 0 sinx – 4sin 3 x + cosx = 0 3 3 sin x cos x sinx cosx− = + ( ) 24sin33cossin8 66 =−+ xxx xxxx cos3sin)sin3(cos3 −=+ 3 3 sin x cos x sinx cosx+ = − 4 4 4 (sin ) 3sin 4 2x cos x x+ + = xxxx sin3cos)cos3(sin3 +=− 8 8 2 17 sin 2 16 x cos x cos x+ = 6 6 2 sin 2 1x cos x cos x+ = − 2) xxxxx cossin4sin 2 1 cossin 44 −=+− 3) 02sin2coscos 23 =−++ xxx 4) ( ) ( ) )cos2(8sin3sin3 2 xxx −=++ 5) 0sincos)cossin1(2cos =+++ xxxxx 6) 06cos6sin3sin 23 =+−− xxx + =sin sin3 sin4x x x + + = sin sin2 sin3 0x x x g. 2cos cos( ) 4sin 2 1 3 x x x π + + = a) x x x x 2cos3 cos21 3sin 2sin4 −= − + b) xxxx 4cossin3cos2sin 2222 +=+ c) 04sin32cos43sin =+−− xxx d) 012sin 2 1 sin2cos3sin 2 =++++ xxxx e) 0 2cos2 cossincossinsincos 2266 = − −++ x xxxxxx g) x xx x xx sin cossin4 cos 1 cot.cos 2 − =+ a) ( ) 0 sin22 3 4 cos 4 sin2cossin2 44 = − − − +++ x xxxx ππ b) ( ) xxxxxxxxx cos.sincossin2cos.2coscotcossin 233 +++=+ c) xgxxxx 22 cot).2cos(cos32coscos10 −=−+ c) ( ) ( ) 2 1 sin 2 cos sin 1 2sinx x x x− − = − d) ( ) ( ) xxxxx sin32sincossin23cos2 −=+− 2 2 2 2 cos cos 2 cos 3 cos 4 2x x x x + + + = a) 0cossin2cos2sincossin1 33 =+−−−−+ xxxxxx b) x xxx 2 2 tan 1 cot.cossin1 =+− c) )cos1(sin2sincos)sin1(1 22 xxxxx ++=++ d) 02cot2cottan2tan 22 =−++− xxxx a) ( ) ( ) 012sin 2sin34 cossincossin8 2 66 =−+ − −+ x x xxxx b) 0sin2cos.3sin 22 =+ xxx c) 0 32cos5 2cos2cossincossin 4466 = − −+++ x xxxxx d) xxxx tan2sintan.sin =+ e) )cos1(sin2sincos)sin1(1 22 xxxxx ++=++ g) xxx 7cos1coscos2 2 −=+ a) 12sinsin)cos1(cos)sin1( 22 −=−−− xxxxx ; b) 21cos3 2 cos 2 sin 2 +=+ − x xx 103. 2 2 2 2sin cos 3 cos 5 cos 2 1x x x x− = − − d) −= − − − 4 5 cos4 2 3 sin 1 2 cos 1 π ππ x xx e) 02cossin2sin2)2cos1(cos3 =+++− xxxxx xxxxxxx cossin3cossin2coscos3sin 2233 +=++ : a) ( ) 3 )cos1)(cos21( sincos21 = +− + xx xx b) 2cos 2cos 3sin3cos2cos2 3 −= +− x x xxx c) 3 cos cossin43cos3 2 = − x xxx 2 sin 2sin 2 2sin 1x x x − + = − cos2x + tanx = 1 sin 4 2 x +cos 4 2 x =1-2sinx cos 3 x+ sin 3 x= cos2x cos 6 x-sin 6 x= 13 8 cos 2 2x cos 8 x+sin 8 x= 1 8 cos 6 x+sin 6 x=cos4x 4 4 sin cos 1 (tan cot ) sin 2 2 x x x x x + = + 102. 2 2 3 3 2 sin 3 sin (cos3 .sin sin 3 .cos ) 3sin 4 sin .sin 3 x x x x x x x x x + + = a) ( ) tan3 tan 72x x= − o b) tan 4 .tan 1x x = − c) 3 tan 2 2;(0 2 )x x+ = < < π d) tan .tan 1 tan .tan tan .tan ;( 2 2 ) 9 9 90 90 x x x π π π π = + + − π < < π e) 2 2 1 tan 2 7;(0 360 ) cos 2 x x x + = < < o f) ( ) 3 2 1 tan 4 3 1 tan 8 7 tan ;( ) cos x x x x x + + + = + −π < < π 3.Tính sin ;cos 10 10 π π sau đó giải phương trình ( ) 10 2 5 tan 5 1;x x+ = − −π < < π a) ( ) ( ) cos 3 sin cos sinx xπ = π b) 4 4 5 sin cos 8 x x+ = c) 6 6 cos sin cos2x x x− = d) 4 6 cos cos 2 2sin 0x x x− + = e) 3 3 5 cos .cos3 sin .sin 3 8 x x x x− = f) 3 3 3 cos .cos3 sin .sin 3 cos 4x x x x x+ = g) 3 3 1 cos .cos3 sin .sin 3 8 x x x x+ = h) 4 4 1 sin cos 4 4 x x π + + = ÷ 1) 2 2cos 3cos 1 0x x− + = 2) 2 cos sin 1 0x x+ + = 3) 3sin 4cos 5x x + = 4) 2sin 2cos 2x x− = 5) 2 1 sin 2 sin 2 x x+ = 6) 5cos 2 12sin 2 13x x − = 7) sin 6 3 cos6 2x x+ = 8) ( ) 2 sin cos 4sin .cos 1x x x x+ = + 9) ( ) sin 2 12 sin cos 12 0x x x− + + = 10) ( ) sin 2 12 sin cos 12 0x x x− − + = 11) 2 2 sin 3sin .cos 2cos 0x x x x+ + = 12) 2 2 2cos 3sin 2 8sin 0x x x+ − = 13) 2 2 2sin 5sin .cos 8cos 2x x x x− − = − 14) ( ) 3 sin cos 2sin 2 3 0x x x+ + + = 15) sin cos 4sin .cos 1 0x x x x − + + = 16) sin 2 12(sin cos ) 12 0x x x− − + = 17) 3 3 sin cos 1x x+ = 18) ( ) 2 2 3sin 8sin .cos 8 3 9 cos 0x x x x+ + − = 19) 2 2 4sin 3 3sin 2 2cos 4x x x+ − = 20) 2 2 1 sin sin 2 2cos 2 x x x+ − = 21) ( ) ( ) 2 2 2sin 3 3 sin .cos 3 1 cos 1x x x x+ + + − = − 22) 2 16sin 6sin 7 0x x− − = 23) 2 9sin 9cos 5 0x x+ − = 24) 2 2 3 sin 2 cos 0 4 x x− + = 25) cos 8 cos 0 4 8 x x − = 26) 3 17 sin cos3 0 2 x x− = 27) 2 5 cos 2 4sin 3 3 2 x x π π + + + = ÷ ÷ 28) ( ) ( ) 2 2 11 14sin 6 5 3cos2 6 5x x− π − = π − 29) 2 tan 5tan 6 0x x− + = 30) 2 1 3cot 1 0 sin x x + + = 31) 2 1 _ tan 3 0 cos x x − = 32) 2 2 5 3 12sin 2cos 4 1 tan x x x − − = − + 33) 2 2 cos12 2cos6 3 0 12 8 x x x − − = − π + π 34) 4 4 5 1 sin cos 0 3 x x− − = 35) cos 2 sin 1 2 x x − = a) 2 10 tan 3 cos 4 3; 1 tan 4 2 x x x x − π π + = < < ÷ + b) ( ) ( ) 1 tan 1 sin 2 1 tanx x x− + = + c) 9 3 sin 2 4tan 2 x x+ = d) 1 cos 2 2sin 2 tan 0 2 x x x+ − + = e) tan 3 tan tan 3 x x x + = − f) 4 2cos8 tan 4 4 x x+ = a) ( ) 2sin 2 3 6 sin cos 8x x x− + = − b) sin 2 2 cos 1 4 x x π + − = ÷ a) ( ) 3 3 sin cos 1 2 2 sin .cosx x x x+ = + − b) cos2 sin cos 1 sin 2 x x x x + = − 1) sin17 .cos3 sin11 .cos9x x x x= 2) sin 5 .sin 4 3 .sin 2x x cox x x= 3) sin sin 2 sin 3 cos cos 2 3x x x x x cox x + + = + + 4) sin 3 sin 5 sin 7 0x x x + + = 5) tan tan 2 tan3x x x + = 6) sin 2 sin 5 cosx x x= − 7) 3 2sin .sin3 3cos 2x x x+ = 8) 2sin .cos3 1 2cos 2 sin 0x x x x− + − = 9) 2 2 2 2 sin sin 2 sin 3 sin 4 2x x x x+ + + = 10) 4 4 3 cos6 sin cos 4 x x x − + = 11) 2 2cos 4 sin10 1x x+ = 12) ( ) ( ) 1 tan 1 sin 2 1 tanx x x− + = + 13) tan tan 2 sin 3 cosx x x x+ = 14) tan 2cot 2 2cot 4x x x+ − 15) sin .sin 4 2cos 3 cos .sin 4 6 x x x x x π = − − ÷ 16) sin sin 2 sin 3 1 cos cos 2x x x x x+ + = + + 17) 2 2 1 sin sin 3 sin .sin 3 4 x x x x+ = 18) ( ) 2cos 2 sin 2 2 sin 2 cosx x x x− = + 19) cos10 cos8 cos6 1 0x x x − − + = 20) cot tan sin cosx x x x − = + 22) ( ) ( ) 2 2 2 2 sin 2 3 cos 2 cos 2 5 sin 6 4 4 x x x x π π + + + = − + − ÷ ÷ 3 8cos ( ) cos3 3 x x π + = 23) 9cos3 .cos5 7 9cos3 .cos 12cos 4x x x x x + = + 24) ( ) 3 2cos13 3 cos5 cos3 8cos .cos 4x x x x x+ + = a) 1 1 2 sin 2 cos sin 4x x x + = b) 2 2sin 3 2 sin sin 2 1 1 0 sin 2 1 x x x x + − + + = + c) 3 2 cot 2 2cot 4 3 sin 2 sin 4 x x x x + = − + d) ( ) 1 2cos 2 2 sin cos sin cos sin cos x x x x x x x = + − − e) ( ) ( ) 2 sin cos 2cos 1 tan sin cos 1 sin sin cos x x x x x x x x x − + − = + − − 1 1 2 2 sin( ) 4 sin cos x x x π + = + a) 2 6 8 2cos 1 3cos 5 5 x x x + = b) 2007 2007 sin cos 1x x+ = c) ( ) 2 2 cos 2 cos 4 4 cos 3x x x− = + a) 2 2 4sin 2 3 tan 3tan 4sin 2 0x x x x− + − + = b) 2 3tan 2 4 tan3 tan 3 .tan 2x x x x− = a) 2sin cot 2sin 2 1x x x+ = + b) 1 3tan 2sin 2x x+ = c) 5sin 3 3sin 5x x= d) 6 6 2 13 cos sin cos 2 8 x x x− = e) ( ) 4 4 sin cos 1 tan cot sin 2 2 x x x x x + = + f) 2 2sin 3 1 8sin 2 .cos 2 4 x x x π + = + ÷ e) 4 4 1 1 cos 2 cos 2 1 2 2 x x− + + = a) 3 3 7 tan 2 tan 3x x+ + − = b) 3 32 2 3 sin cos 4x x+ = f) 2 sin sin sin cos 1x x x x+ + + = c) 2 2 sin 2 sin sin 2 sin 3x x x x+ − + − = d) 2 2 4 4 10 8sin 8cos 1 1x x+ − − = − + = −(2cos 1)(2sin cos ) sin2 sinxx x x + + + + = 1 sin cos sin2 cos2 0x x x x − + =(2cos 1)(sin cos ) 1x x x + − + = 2 2sin cos 2cos (sin cos ) 1x x x x x + = 3 3 3 sin cos3 cos sin3 sin 4x x x x x + = 3 3 2 s cos3 sin sin3 4 co x x x x π π − = + 3 1 3 sin( ) sin( ) 10 2 2 10 2 x x π π − = +sin(3 ) sin2 sin( ) 4 4 x x x + + + + =5 2sin 8 os sin2 3cos2 0x c x x x + − = + 1 cos sin cos2 sin2x x x x − + − + = cos2 4cos 2sin2 8sin 1 0x x x x − = + −2sin2 cos2 7sin 2cos 4x x x x + − + = 9sin 6cos 3sin2 cos2 8x x x x − = − +sin2 cos2 3sin 2 cosx x x x + − = − sin2 4cos 1 sin 2cos2x x x x + − − − =sin2 cos2 3sin cos 2 0x x x x − + = 1 2cos2 8cos 7 cos x x x − = −4sin3 4cos2 5(sin 1)x x x 2 (2sin 1)(2sin 2 1) 3 4cosx x x − + = − 2 (2sin 1)(3cos4 2sin 4) 4cos 3x x x x + + − + = 2 3 cos sin cos 0x x x + + = 13) cos3 cos 4 cos5 0x x x − + = + + − − = sin2 cos2 3sin cos 2 0x x x x 1) sin sin 6 x π = ; 2) 2 cos cos 3 x π = 3) tan tan 6x π = 4) 7 cot cot 2 x π = 5) sin 2 sin 2 x x π = − ÷ 6) cos3 cosx x = ; 7) ( ) tan 5 tan 7 x π + = 8) ( ) cot 3 cot 2 x x π − = + ÷ 9) sin cosx x = 10) sin cos 0x x + = 11) 2 2 tan cot 0x x− = 12) 2 2 tan cot 2 0x x+ − = 10) 8cos 2 sin 2 cos4 2x x x = 11) tan 2 2tan 0x x − = 12) 2 2cos cos2 2x x+ = 5) 3tan 3cot 3 3 0x x+ − − = ; 6) 2 2 2 2 sin 2 2 tan sin 2 4cos x x x x − = − 7) 1 2 tan cot 2sin 2 sin 2 x x x x + = + 4) ( ) 1 4sin 3cos 4 1 tan cos x x x x + = + − ; c: 1 3 sin cos 3 3 sin cos 1 x x x x + = + + + 1) 03) 4 sin(2cos222sin =++++ π xxx ; 2) 07cos2sin 2 5 cos 2 sin 2 3 cos 2 7 sin =++ xx xxxx ; 3) 6 cos.3) 2 3(cos) 2 2(cos) 2 (cos 222 ππππ =−++++ xxx =sin7 sin sin3 sin5x x x x 6) 12sincossin2 +=+ xxx . 3/ tanx sin 2 x-2sin 2 x=3(cos2x+sinxcosx) 1. 3 2sin cos2 cos 0x x x+ + = ; 8. 2 2 2 sin ( ). cos 0 2 4 2 x x tg x π − − = ; 2. 2 2 7 sin .cos4 sin 2 4sin ( ) 4 2 2 x x x x π − = − − ; 9. 2 cos (cos 1) 2(1 sin ) sin cos x x x x x − = + + ; 3. 9sin 6cos 3sin2 cos2 8x x x x+ − + = ; 10. − = 1 tan2 tan cos .sin3 3 x x x x ; 4. 4 4 sin cos 1 1 cot 2 5sin2 2 8sin2 x x g x x x + = − ; 11. 1 2cos2 8cos 7 cos x x x − + = ; 5. − + = 2 4 4 (2 sin 2 )sin3 tan 1 cos x x x x ; 12. − = + − + 2 cos2 1 cot 1 sin sin2 1 tan 2 x x x x x 108. 2 2 cos3 2 cos 3 2(1 sin 2 )x x x+ − = + 104. 2 2sin ( ) 1 sin 6 0 3 x x π + + − = 2 2 2 sin sin 3 2sin 2x x x + = 109. sin cos 2(2 sin 2 )x x x+ = − 110. 2009 2009 sin cos 1x x+ = 6. − + + =3 tan (tan 2sin ) 6cos 0x x x x ; 13. − + = 2 cot tan 4sin2 sin2 x x x x ; 7. + − = 2 cos2 cos .(2tan 1) 2x x x 21) ( ) ( ) sin 3 cos 2sin 3 cos3 1 sin 2cos3 0x x x x x x− + + − = 14. + − = + 2 tan cos cos sin .(1 tan .tan ) 2 x x x x x x . 1/ 2sin15x+ 3 cos5x+sin5x=k víi k=0 vµ k=4 víi k=0 6/ sin3x+2cos2x-2=0 7/ a/ tanx+ 3 cot x -2 = 0 b / 2 4 cos x +tanx=7 c * / sin 6 x+cos 4 x=cos2x 8/sin( 5 2 2 x π + )-3cos( 7 2 x π − )=1+2sinx 9/ 2 sin 2sin 2 2sin 1x x x − + = − 10/ cos2x+5sinx+2=0 11/ tanx+cotx=4 12/ 2 4 sin 2 4cos 2 1 0 2sin cos x x x x + − = 16/ 2cosx- sin x =1 13/ sin 1 cos 0x x+ + = 14/ cos2x+3cosx+2=0 2/ sin 3 x+cos 3 x=2sinxcosx+sin x+cosx 15/ 2 4 4sin 2 6sin 9 3cos2 0 cos x x x x + − − = b: 6 4sin 3cos 6 4sin 3cos 1 x x x x + + = + + 2/ a : 1 3 sin cos cos x x x + = 3/ cos7 3 sin 7 2 0x x − + = *t×m nghiÖm 2 6 ( ; ) 5 7 x π π ∈ 4/( cos2x- 3 sin2x)- 3 sinx-cosx+4=0 5/ 2 1 cos cos2 cos3 2 (3 3 sin ) 2cos cos 1 3 x x x x x x + + + = − + − 6/ 2 cos 2sin .cos 3 2cos sin 1 x x x x x − = + − 1/ sin 4 2 x +cos 4 2 x =1-2sinx 10/ sin cos 4sin 2 1x x x − + = c/3 sin 2 x+5 cos 2 x-2cos2x-4sin2x=0 9/sin 3 (x- π /4)= 2 sinx 3/ 1- sin 3 x+cos 3 x= sin2x 1/ a/1+tanx=2sinx + 1 cos x b/ sin x+cosx= 1 tan x - 1 cot x 11/ cosx+ 1 cos x +sinx+ 1 sin x = 10 3 4/ 2sinx+cotx=2 sin2x+1 5/ 2 sin2x(sin x+cosx)=2 6/ (1+sin x)(1+cosx)=2 7/ 2 (sin x+cosx)=tanx+cotx 8/1+sin 3 2x+cos 3 2 x= 3 2 sin 4x 9/ * a* 3(cotx-cosx)-5(tanx-sin x)=2 9/b*: cos 4 x+sin 4 x-2(1-sin 2 xcos 2 x) sinxcosx-(sinx+cosx)=0 12/ sinxcosx+ sin cosx x + =1 18/cos10x+2cos 2 4x+6cos3xcosx=cosx+8cosxcos 2 3x 1/ sin 2 x+sin 2 3x=cos 2 2x+cos 2 4x 2/ cos 2 x+cos 2 2x+cos 2 3x+cos 2 4x=3/2 4/ cos3x+ sin7x=2sin 2 ( 5 4 2 x π + )-2cos 2 9 2 x 5/ sin 2 4 x+ sin 2 3x= cos 2 2x+ cos 2 x víi (0; )x π ∈ 6/sin 2 4x-cos 2 6x=sin( 10,5 10x π + ) víi (0; ) 2 x π ∈ 7/ cos 4 x-5sin 4 x=1 8/4sin 3 x-1=3- 3 cos3x 9/ sin 2 2x+ sin 2 4x= sin 2 6x 10/ sin 2 x= cos 2 2x+ cos 2 3x 11/ (sin 2 2x+cos 4 2x-1): sin cosx x =0 12/ 4sin 3 xcos3x+4cos 3 x sin3x+3 3 cos4x=3 ; 24 2 8 2 k k x π π π π = + + 13/ 2cos 2 2x+ cos2x=4 sin 2 2xcos 2 x 14/ cos4xsinx- sin 2 2x=4sin 2 ( 4 2 x π − )-7/2 víi 1x − <3 3/sin 2 x+ sin 2 3x-3 cos 2 2x=0 15/ 2 cos 3 2x-4cos3xcos 3 x+cos6x-4sin3xsin 3 x=0 16/ sin 3 xcos3x +cos 3 xsin3x=sin 3 4x 5) xxxx 2sin3cos8sin7cos −=+ 91. 2 2 2sin 2 10sin 2 cos4 40cos 1 0x x x x− + + + = 17/ * 8cos 3 (x+ 3 π )=cos3x 19/ sin 5 5sin x x =1 ( ) + =tan 3 2 3x ; 2 2 x π π − ∈ ÷ 20 / cos7x+ sin 2 2x= cos 2 2x- cosx 21/ sin 2 x+ sin 2 2x+ sin 2 3x=3/2 22/ 3cos4x-2 cos 2 3x=1 2/ cos 3 x-sin 3 x=cos 2 x-sin 2 x 11/ 1+ sinx+ cos3x= cosx+ sin2x+ cos2x 3/ cos 3 x+ sin 3 x= cos2x 4/ 4 4 sin cos 1 (tan cot ) sin 2 2 x x x x x + = + v« nghiÖm 5/cos 6 x-sin 6 x= 13 8 cos 2 2x 6/sin 4 x+cos 4 x= 7 cot( )cot( ) 8 3 6 x x π π + − 7/ cos 6 x+sin 6 x=2(cos 8 x+sin 8 x) 8/cos 3 x+sin 3 x=cosx-sinx 9/ cos 6 x+sin 6 x=cos4x 10/ sinx+sin 2 x+sin 3 x+sin 4 x= cosx+cos 2 x+cos 3 x+cos 4 x 11/ cos 8 x+sin 8 x= 1 8 12/ (sinx+3)sin 4 2 x -(sinx+3) sin 2 2 x +1=0 1/ cos2x- cos8x+ cos4x=1 2/sinx+2cosx+cos2x-2sinxcosx=0 3/sin2x-cos2x=3sinx+cosx-2 4/sin 3 x+2cosx-2+sin 2 x=0 5/ 3sinx+2cosx=2+3tanx 6/ 3 2 sin2x+ 2 cos 2 x+ 6 cosx=0 7/ 2sin2x-cos2x=7sinx+2cosx-4 8/ sin3 sin 5 3 5 x x = 9/ 2cos2x-8cosx+7= 1 cos x 10/ cos 8 x+sin 8 x=2(cos 10 x+sin 10 x)+ 5 4 cos2x 12/ 1+sinx+cosx+sin2x+cos2x=0 13/ sin 2 x(tanx+1)=3sinx(cosx-sinx)+3 14/ 2sin3x- 1 sin x =2cos3x+ 1 cos x 15/cos 3 x+cos 2 x+2sinx-2=0 16/cos2x-2cos 3 x+sinx=0 17/ tanx–sin2x-cos2x+2(2cosx- 1 cos x )=0 18/sin2x=1+ 2 cosx+cos2x 19/1+cot2x= 2 1 cos 2 sin 2 x x − 10/a* tan2x+sin2x= 3 2 cotx 20/ 2tanx+cot2x=2sin2x+ 1 sin 2x 21/cosx(cos4x+2)+ cos2x-cos3x=0 b* (1+sinx) 2 = cosx 22/ 1+tanx=sinx+cosx 23/ (1-tanx)(1+sin2x)=1+tanx 24/ 2 2 sin( ) 4 x π + = 1 1 sin cosx x + 25/ 2tanx+cotx= 2 3 sin 2x + 26/ cotx-tanx=cosx+sinx 27/ 9sinx+6cosx-3sin2x+cos2x=8 1/ sin 3 xcosx= 1 4 + cos 3 xsinx 2/ cosxcos2xcos4xcos8x=1/16 3/tanx+2cot2x=sin2x 4/sin2x(cotx+tan2x)=4cos 2 x 5/ sin4x=tanx 6/ sin2x+2tanx=3 7/ sin2x+cos2x+tanx=2 8/tanx+2cot2x=sin2x 9/ cotx=tanx+2cot2x 1/ sin8x+ cos4x=1+2sin2xcos6x 2/cosx+cos2x+cos3x+cos4x=0 3/ sin 3 sin sin 2 cos2 1 cos 2 x x x x x − = + − t×m ( ) 0;2x π ∈ 4/ sinx+sin2x+sin3x+sin4x=0 5/ sin5x+ sinx+2sin 2 x=1 6/ ( ) 3 cos 2 cot 2 4sin cos cot 2 cos 2 4 4 x x x x x x π π + = + − ÷ ÷ − 7/ tanx+ tan2x= tan3x 8/ 3cosx+cos2x- cos3x+1=2sinxsin2x 1/ sin( 3 10 2 x π − )= 1 2 sin( 3 10 2 x π + ) 3 4 14 2 ; 2 ; 2 5 15 15 x k k k π π π π π π = + + + 2/ sin( 3 4 x π − )=sin2x sin( 4 x π + ) 4 2 x k π π = + 3/(cos4x/3 – cos 2 x): 2 1 tan x − =0 3x k π = 4/ cosx-2sin( 3 2 2 x π − )=3 4x k π = 5/ cos( 7 2 2 x π − )=sin(4x+3 π ) ; 6 2 k x k π π π = ± + 6/3cot 2 x+2 2 sin 2 x=(2+3 2 )cosx 2 ; 2 3 4 x k k π π π π = ± + ± + 7/2cot 2 x+ 2 2 cos x +5tanx+5cotx+4=0 4 x k π π = − + 8/ cos 2 x+ 2 1 cos x =cosx+ 1 cos x x k π = 9/sinx- cos2x+ 1 sin x +2 2 1 sin x =5 7 2 ; 2 ; 2 2 6 6 x k k k π π π π π π = + − + + 11/ 1 sin 2 1 sin 2 x x + − +2 1 tan 1 tan x x + − =3 { } ; , tan 2x k k π α π α = + = 1/ 3 4 6 (16 3 8 2)cos 4cos 3x x + − − = − 2 4 x k π π = ± + 2/cos ( ) 2 3 9 16 80 4 x x x π − − − =1 t×m n 0 x ∈ Z { } 21; 3x = − − 3/ 5cos cos2x x − +2sinx=0 2 6 x k π π = − + 4/3cotx- tanx(3-8cos 2 x)=0 3 x k π π = ± + 5/ ( ) 2 sin tan 2cos 2 tan sin x x x x x + − = − 2 2 3 x k π π = ± + 6/sin 3 x+cos 3 x+ sin 3 xcotx+cos 3 xtanx= 2sin 2x 2 4 x k π π = + 7/tan 2 xtan 2 3 xtan 2 4x= tan 2 x-tan 2 3 x+tan4x 4 k x π = 8/tanx+tan2x=-sin3xcos2x 2 3 k x k π π π = + 9/sin3x=cosxcos2x(tan2x+tan 2 x) x k π = 10/ 2 sin sin 1 sin cosx x x x+ = − − 5 1 ;sin 2 x k x π − = = 11/cos 2 ( ) 2 sin 2 cos 4 x x π + -1=tan 2 2 tan 4 x x π + ÷ 2 4 x k π π = − + b/ 12/ 2 3 2 cos 6 sin 2sin 2sin 5 12 5 12 5 3 5 6 x x x x π π π π − − − = − − + ÷ ÷ ÷ ÷ 5 5 5 5 ; 5 ; 5 12 3 4 x k k k π π π π π π = − + − + + 1/ cos3x+ 2 2 cos 3x − =2(1+sin 2 2x) x k π = 2/ 2cosx+ 2 sin10x=3 2 +2sinxcos28x 4 x k π π = + 3/ cos 2 4x+cos 2 6x=sin 2 12x+sin 2 16x+2 víi x ( ) 0; π ∈ 4/ 8cos4xcos 2 2x+ 1 cos3x− +1=0 2 2 3 x k π π = ± + 5/ sin cos x x π = 0x = 6/ 5-4sin 2 x-8cos 2 x/2 =3k t×m k ∈ Z * ®Ó hÖ cã nghiÖm 7/ 1- 2 2 x =cosx 8/( cos2x-cos4x) 2 =6+2sin3x 2 x k π π = + 9/ ( ) 1 1 cos 1 cos cos 2 sin 4 2 x x x x − + + = 2 4 x k π π = ± + [...]... phương trình Bài 39 D03-DB2.Giải phương trình Bài 40 A04-DB1.Giải phương trình Bài 41 B04-DB1.Giải phương trình Bài 42 D04-DB1.Giải phương trình Bài 43 A04-DB2.Giải phương trình Bài 44 B04-DB2.Giải phương trình Bài 45 D04-DB2.Giải phương trình Bài 46 A05-DB1.Giải phương trình Bài 47 B05-DB1.Giải phương trình Bài 48 D05-DB1.Giải phương trình Bài 49 A05-DB2.Giải phương trình Bài 50 B05-DB2 Bài 51 D05-DB2.Giải... trình Bài 52 A06-DB1.Giải phương trình Bài 53 B06-DB1.Giải phương trình Bài 53 D06-DB1.Giải phương trình Bài 54 A06-DB2.Giải phương trình Bài 55 B06-DB2.Giải phương trình Bài 56 D06-DB2.Giải phương trình Bài 57 TK1A07.Giải phương trình Bài 58 TK2A07.Giải phương trình Bài 59 TK1B07.Giải phương trình Bài 60 TK2B07.Giải phương trình Bài 61 TK1D07.Giải phương trình Bài 62 TK2D07.Giải phương trình Bài 63... cos3x = 0 Bài 27 A02-DB1 Tìm nghiệm thuộc khoảng (0 ; 2pi) của phương trình Bài 28 A02-DB1 1 − cos 2 x sin 2 2 x Bài 29 B02-DB1.Giải phương trình Bài 30 D02-DB1.Giải phương trình Bài 31 A02-DB2.Giải phương trình Bài 32 B02-DB2.Giải phương trình Bài 33 D02-DB2 Bài 34 A03-DB1.Giải phương trình Bài 35 B03-DB1.Giải phương trình Bài 36 D03-DB1.Giải phương trình Bài 37 A03-DB2.Giải phương trình Bài 38 B03-DB2.Giải... sin 2 x + sin 4 x = sin 6 x 5 sin 8 x + cos8 x = (sin10 x + cos10 x) + cos 2 x 4 11 cos5 x sin 4 x = sin 5 x cos 4 x 1 sin 7 x + cos5 x + (sin 5 x + cos3 x)sin 2 x = sin x + cos x 2 cos 2 x sin 5 x = cos 2 x cos8 x 111 cos13 x + sin14 x = 1 106 sin 2 x + 2 = sin 2 3 x + 2sin x sin 2 4 x + sin 2 3 x = sin 2 2 x + sin 2 x 112 2|sin x| + | sin x |= cos x − cos 2 x + 1 3sin 4 x + 5cos 4 x − 3 = 0 cos 6... TK1B07.Giải phương trình Bài 60 TK2B07.Giải phương trình Bài 61 TK1D07.Giải phương trình Bài 62 TK2D07.Giải phương trình Bài 63 A08-DB1.Giải phương trình Bài 64 A08-DB2.Giải phương trình Bài 65 B08-DB1.Giải phương trình Bài 66 B08-DB2.Giải phương trình Bài 67 D08-DB1.Giải phương trình ... khoảng ( 0; 2π ) của phương trình : 5 sinx + ÷ = 3 + cos 2 x 1 + 2sin 2 x 11/ Cho phương trình : cos 2 x − (2m + 1) cos x + m + 1 = 0 (*) π 3π a/ Giải phương trình khi m = 3/2 b/ Tìm m để phương trình (*) có nghiệm trên khoảng ; ÷ 2 2 2/ 3/ 4/ Đs: 5/ 6/ 7/ Tìm các gt của thsố m để các pt sau có ng: 8/ 9/ 10/ 11/ 12/ Tìm các gt của thsố m để các pt sau có ng: 13/ 14) 18) 19) Của (*) Hãy... − m ) cos x = 4 có nghiệm thuộc ; ÷ 4 2 35/ tìm tập xác đònh của các hàm số sau: cos x tan x 2 1) y = sin x.tan x ; 2) y = tan x cot x ; 3) y = ; 4) y = ; 5) y = ; sin x − 1 cos x − 1 2 cos x − 1 3π π 2 2 6) y = ; 7) y = ; 8) y = tan 2 x − ÷; 9) y = cot 3x − ÷ ; 4 4 cos x − sin x tan x − sin x 2x sin x tan x cot x 10) y = ; 11) y = ; 12) y = ; 2 2 sin 2 x − cos x sin x − cos x... = 0 7) cos 2 2 x = sin 2 2 x − 3 sin 4 x + 2 1 11 = 9) cos(2 x − 18o )tg 50o + sin(2 x − 18o ) = 2 cos130o 1 cosx + sinx = cos2x 12) 4(sin 4 x + cos 4 x) + 3 sin 4 x = 2 17)tanx-3cotx=4(sinx+ 3 cosx) 1 2 8) 3 cos x + sin 4 x cos x = sin x cos 4 x + 4 cos3 x − 10) sin(15o + x) + cos(45o + x) + = 0 2 2 cos4x+sin4x-2(1-sin2xcos2x)+sinxcosx-(sinx+cosx)=0 11) sinx(1-sinx)=cosx(cosx-1) 15) sin x + 3 cos x... cosx 1) gi¶i ph¬ng tr×nh k= 2 2) T×m k ®Ĩ pt cã nghiƯm Bµi 9)§¹i häc KTÕ QD©n: T×m nghiƯm pt cos7x - 3 sin7x = - 2 2 6 tho· m·n: Π . cos2 cos8x x x x 2 2 2 2 sin 4 sin 3 sin 2 sinx x x x + = + 111 . 13 14 cos sin 1x x+ = 106. 2 2 sin 2 sin 3 2sinx x x+ = + 112 . |sin | 2 2 | sin | cos cos 1 x x x x+ = − + 4 4 3sin 5cos. + ÷ 9) sin cosx x = 10) sin cos 0x x + = 11) 2 2 tan cot 0x x− = 12) 2 2 tan cot 2 0x x+ − = 10) 8cos 2 sin 2 cos4 2x x x = 11) tan 2 2tan 0x x − = 12) 2 2cos cos2 2x x+ = . 3 tan 3 cot 4x x+ + + = . a. cos5xcos3 = cosxcos7x b. sin2x - cos5x = cosx - sin6x c. cosx + cos11x = cos6x d. sinx + sin2x + sin3x = cosx + cos2x + cos3x + + + + + =sin sin2 sin3 sin4 sin5 sin6