! "#$ % & & & '! ( ) *+,(-#./011(23 4 5 678179:.;<!=/01 (678179 >/?(@AB'C/ /011)C/ 5 D C/E@AFB(G#3 /0111)C/ H I#$/0111)C/ (G#3 5 D % DJK D DJK D LJK M KJK N.O PEQ/;) R21(234NSH/)JTSK/)P*+,(234N:.T7.R 1 / # 5P2U:VTWOONJ1/XR 1P AB AC DE DC = AB DE BC DC = / AB DE BE CE = # AB AD DE BE = DP2U:V5PN7.1B'C//01 A U 1 AB BI AC BC = AB AC BC CI = / AB BI AC IC = # AB CI AI AC = LP2U:VDPN11)C/Y:.YZ(G#3:[1!J+!\E1R 1SZ OOZ / MNP RQP∆ = ∆ #=1JJ/(]!(^ _P2U:VLWJ`7.E!( )/01NJP(X a 5 L N 1 ABC AEF∆ ∆ b2*+,cS AEF ABC ∆ ∆ b2*+,cS5 / AEF ABC∆ ∆ b2*+,cS # AFE ABC ∆ ∆ b2*+,cS5 5DL HP11)C/N:.dNdd(G#31!!R 1 A B B C AB BC ′ ′ ′ ′ ′ = B C BC ′ ′ ′ ′ ′ = / ′ ′ ′ ′ ′ = MPC//'!+1!(^1\+1 P11)C/(G#3Ue1!P 5P11)C/:!/'7!(G#3:[1!P DP11)C/e1!U(G#3:[1!P LP*+,/!:/0111)C/(G#3e*+,(G#3/011 1)C/(XP NPf&!MJ_(g !!"#$ 5DJ_(P 21)C/N:!3J(@A/12P hiYJZ7j7@F7.E!( )/01NJ k)R 1 %& % J_( hiYJZ7j7@F7.E!( )/01NJP k)R %'& %&( J_( D21)C/N/XNS/)JSK/)PEl/3N7?\( )+12/2 SH/)J:V(@A4<!1:.+2+2:[/QN3J:V(@A4 <!1:.+2+2:[N/Q3YP>/!:kC/YP5J_( mYm !EQ/;))5J_( *+ , /. 0 1 1 B C A E D I B C A F E B C A 6 3 2 x P M N Q R a 5 L N *+) NOf7!R "#$) 2 !! AN AM NC MB ⇒ = "3455678$ 9:7811*+0 9:7811*+ B A C Q H P 0 !# )HBA ABC∆ ∆ :;<1 = AHB BAC B chung HBA AB C = = ⇒ ∆ ∆ !# BPH AQH∆ ∆ !#;<1) BPH cân tai P AQH cân tai Q HAQ PBH BPH AQH ∆ ∆ = ⇒ ∆ ∆ *+ *+ *+ *+ > - - - "6 ') 9:7811*+0 A B C M N P 9 !#;<1 '?55 9 >+@A0 'B 9 "6;<1 1# 9 "3455678 '=1# 9999999999999999999999999999999999999999999999999999999999 . AHB BAC B chung HBA AB C = = ⇒ ∆ ∆ !# BPH AQH∆ ∆ !#;<1) BPH cân tai P AQH cân tai Q HAQ PBH BPH AQH ∆ ∆ = ⇒ ∆ ∆ *+. ′ ′ = MPC//'!+1!(^1+1 P11)C/(G #3 Ue1!P 5P11)C/:!/'7!(G #3 :[1!P DP11)C/e1!U(G #3 :[1!P LP*+,/!:/0111)C/(G #3 e*+,(G #3 /011 1)C/(XP NPf&!MJ_(g . 9:7 8 11*+0 9:7 8 11*+ B A C Q H P 0 !# )HBA ABC∆ ∆ :;<1 =