... 0 . Sin10 0 .Cos20 0 .Cos40 0 (0,25 đ) = 2 1 2 Cos10 0 . Sin10 0 .Cos20 0 .Cos40 0 = 2 1 Sin20 0 Cos20 0 .Cos40 0 = 4 1 Sin40 0 .C0s40 0 = 8 1 Sin80 0 = 8 1 Cos10 0 (0,25đ) => A = 8 1 (0,25đ) ... 2x +1 = 0 (0,25đ) <=> (x -1) 2 = 0 ( 0,25đ) <=> x = 1 (0,25 đ) C ©u 3: (1 đ) Ta c ã Sin70 0 =Cos20 0 Sin50 0 =Cos40 0 (0,25đ) A = Sin10 0 .Cos20 0 .Cos40 0 =>Cos10 0 .A = Cos10 ... ≤+−+−− −> 0)3)(3( )1( 3 2 mmm m (0,25đ) <=> ≤+− −> 04 3 2 mm m <=> + ≤≤ − −> 2 17 1 2 17 1 3 m m <=> 2 17 1 2 17 1 + ≤≤ − m (0,25đ) C©u 2: (1, 5đ) V× x 2 – 2x...