xet tam giac DFC va tam giac DEB có
DB=DC
D CHUNG
GÓC DFC= GOC DEB
=> TAM GIÁC DEB = TAM GIÁC DFC(GCG)
B,XÉT TAM GIÁC AED VÀ TAM GIÁC AFD CO
AD CHUNG
AF=AE
GÓC AFD = GÓC AED
=> TAM GIÁC AED = TAM GIÁC AFD (CGC)
xet tam giac DFC va tam giac DEB có
DB=DC
D CHUNG
GÓC DFC= GOC DEB
=> TAM GIÁC DEB = TAM GIÁC DFC(GCG)
B,XÉT TAM GIÁC AED VÀ TAM GIÁC AFD CO
AD CHUNG
AF=AE
GÓC AFD = GÓC AED
=> TAM GIÁC AED = TAM GIÁC AFD (CGC)
CHO TAM GIÁC ABC CAN TAI A GOI D LA TRUNG ĐIỂM CANH BC KẺ DE VUONG GOC AB, DE VUONG GOC AC
CMR: TAM GIAC DEB=TAM GIAC DFC
b) tam giac AED=TAM GIAC AFD
C) AD LA TIA PHAN GIAC CUA GOA BAC
1. cho tam giac ABC can tai A, ve diem M, Nbat ki tren duong trung truc ca doan thang BC.CM:
a,tam giac MBCcan tai M
b, MNC=MNB
2.cho tam giac ABC cao M la trung diem cua canh BC. qua B ke duong thang Bx \\ AC, qua C ke Cy \\ AB. giao diem cua Cy, Bx la D. CM: A, D, M thang hang.
3. do dai 2 canh goc vuong cua mot tam giac vuong ti le voi 7 va 24. chu vi tam giac bang 112. tinh do dai canh huyen.
4.cho tam giac ABC can tai A, canh day nho hon canh ben. duong trung truc cua AC cat BC tai M. tren tia doi cua AM lay N \ AN = BM.
a, CM: 2 goc AMC va BAC bang nhau
b, CM: CM = CN
c, de CM vuong voi CN hi tam giac ABC phai co them dieu kien gi?
5. cho tam giac ABC deu. tren tia doi cua tia phan giac goc BAC lay D \ AD = AB. tinh cac goc cua tam giac DBC.
Cho tam giac ABC vuong tai A co AB=3cm;AC=6cm
a,tinh BC
b,Goi E la trung diem cua AC,phan giac cua goc A cat BC tai D.Chung minh tam giac ABD=tam giac AED
c,ED cat AB tai M.Chung minh tam giac BAC= tam giac EAM.Suy ra tam giac MAC vuong can
Cho tam giac ABC vuong tai A. Tia phan giac cua goc ABC cat AC tai D, E la diem tren canh BC sao cho BE = BA. DE vuong goc voi BC
a) Chung minh rang tam giac ABD = tam giac EBD
b) Chung minh rang DE vuong goc voi BC
cho tam giac ABC can tai B .Ke AM vuong BC va CN vuong BA.
a)CM: tam giac BAM =tam giac BCN
b)Goi O la giao diem cua AM va CN. CM :tam giac NOA =tam giac MOC.
c)CM:BO la phan giac goc ABC .
d)Lay diem H sao cho AC la trung truc cua doan thanng OH. Tim dieu kien cua tam giac ABC de tam giac OCH deu.
Cho tam giac ABC vuong tai B. Goi D la trung diem cua canh AC. Tren tia doi cua tia DB lay diem E sao cho DB = DE. Chung minh:
a) tam giac ADE = tam giac CDB
b) AE // BC
c) tam giac ACE vuong
d) EC vuong goc CB
cho tam giac abc co goc bac=75do.goc abc=35do.phan giac cua goc bac cat canh bc tai d .duong thang qua a va vuong goc voi ad tai e.goi m la trung diem cua de .cmr:
a, tam giac acm la tam giac can
b, ab<\(\frac{ad+ae}{2}\)
c, cu vi tam giac abc bang do dai doan thang be
cho tam giac ABC ,A=90 do .BD la phan giac cua B , D thuoc AC . DE vuong goc BC tai E . AB cat DE tai F . chung minh
a, BD la duong trung truc cua AE
b, tam giac DFC can
c, AE song song FC
d, AD be hon DC
Cho tam giac ABC vuong tai A co AB=AC . Goi D la trung diem cua AC . Tren tia doi cua tia DB lay diem E sao cho DB=DE
a) Chung minh : tam giac ADB=tam giac CDE
b) Tren tia doi cua tia AB lay diem I sao cho AD = AI. chung minh : tam giac CDE = tam giac AIC
c) chung minh CI vuong goc EB