cho tg ABC co ba goc nhon . duong cao BE, CF cat nhau tai O. duong tron tam O duong kinh AB cat CF tai M. duong tron tam O duong kinh AC cat BE tai N. CM: tg AMN can
Cho tam giac ABC nhon, ba duong cao AD,BE,CF cat nhau ta H.Qua A ve cac duong thang song song voi BE,CF lan luot cat cac duong thang CF,BE tai P,Q. Cmr
a, AE.AC=AF.AB
b, PQ vuong goc voi trung tuyen AM cua tam giac ABC
Cho tam giac ABC nhon ( AB<AC) hai duong cao BE va CF cat nhau tai H. Ve duong thang vuong goc voi AB tai B, ve duong thang vuong goc voi AC tai C, hai duong thang nay cat nhau tai D.
a. C/M AH vuong goc BC và BCHD là hinh binh hanh
b. Goi M la trung diem BC. C/M : H,M,D thang hang
c. Goi K la diem doi xung cua H qua BC. C/M BD=CK
Cho tam giac ABC nhon , cac duong cao AD, BE,CF cat nhau tai H, ve DM vuong goc AC tai M. Goi K la giao diem CH va DM
C/m : CD/BD=CM/EM va BH/EH=DK/MK
cho tam giac ABC co 3 goc nhon ,cac duong cao AD,BE,CF cat nhau tai H .chung minh tam giac ABE dong dang voi tam giac ACF. chung minh HE.HB=HC.HF . chung minh goc AEF bang goc ABC
cho tam giac ABC nhon co 3 duong cao AD , BE , CF cat nhau tai H CMR a)DB*DC=DH*DA.b)tam giac ABC dong dang voi tam giac AEF.c)DH/AD +HE/BE+HF/CF=1.d) H la giao diem cac duong phan giac cua tam giac DEF
cho tam giac ABC co 3 goc nhon hai duong cao BE vaCF cat nhau tai H . chung mnhAH vuong goc voiBC tai D
Cho tam giac nhon ABC,cac duong cao AD,BE,CF cat nhau tai H a,Chung minh :tam giac AEB va tam giac AFC dong dang .Tu do suy ra:AF.AB=AE.AC b,Chung minh :goc AEF= goc ABC c,Cho AE=3cm,AB=6 cm.Chung minh rang : SABC=4SAEF
Cho tam giac ABC nhon. ve duong cao BD, CE.tia phan giac cua ABD, ACE cat nhau tai O va cat AC va AB tai N,M. BN cat CE tai K, CM cat BD tai H. CMR:
a, BN vuong goc voi CM.
b, MNHK la hinh thoi.