Hình:
a) Xét \(\Delta AMB\) và \(\Delta KMC\) có:
\(MA=MK\left(gt\right)\)
\(MB=MC\) (do M là trung điểm BC)
\(\widehat{M_1}=\widehat{M_2}\) (2 góc đối đỉnh)
\(\Rightarrow\Delta AMB=\Delta KMC\left(c.g.c\right)_{\left(1\right)}.\)
b) Từ \(_{\left(1\right)}\Rightarrow\widehat{A}=\widehat{K}\) (2 góc tương ứng).
mà \(\widehat{A};\widehat{K}\) ở vị trí so le trong.
\(\Rightarrow\) AB // KC.
Cho tam giac ABC co goc B=goc C, goi I la trung diem cua canh BC. Tren canh AB lay diem D, tren tia DI lay diem E sao cho I la trung diem cua DE. CM:
a) BD=CE
b) CB la tia phan giac cua goac ACE
Cho tam giac ABC can tai A, tren AB lay D, tren tia doi cua tia CA lay E sao cho BD=CE. Noi D vs E. Goi I la trung diem cua DE. CM: B,I,C thang hang
cho tam giac ABC co AB<AC,M la trung diem cua BC.tren doan thang AM lay diem I bat ki(I \(\ne\)A;I\(\ne\)M)lay diem D tren tia doi cua MA sao cho MD=MI
a.chung minh tam giac MIB=MDC
b/Chung minh BI song song DC,BD song song IC
cho tam giac ABC can tai A tren tia doi cua tia bc lay diem M tren tia doi cua tia CB lay diem N sao cho BM=Cn
cho tam giac ABC can o A co goc A =40 do . duong trung trc AB cat BC o D
a, tam giac ABD la tam giac gi ? vi sao?
b, tinh goc BAD; goc CAD
c, tren tia doi cua tia AD lay diem M sao cho AM=CD CM: tam giac BMD la tam giac can
cho tam giac ABC VUONG CAN TAI A TREN TIA DOI CUA TIA BA LAY DIEM E SAO CHO BE=BC
A) TINH SO DO GOC CUA TAM GIAC AEC
B) TREN TIA DOI CUA TIA BC LAY DIEMF SAO CHO BF= BC TINH SO DO GOC CUA TAM GIAC CEF
CAC BAN LAM GIUP MINH VOI
Cho tam giac ABC can tai A.Tren can AB lay diem D,tren can AC lay diem E sao cho AD=AE.Goi M la giao diem cua BD va CD. Chung minh:
a) cac hinh chieu cua BD va CE tren BC bang nhau
b) BE=CD
c) tam giac BMD =tam giac CME
d) AM la tia p/g cua goc BAC
e) BE nho hon BC+DE:2
giup mk nha m. n can gap tick Cho
tam giac abc co hai duong trung tuyen bm va cn .tren tia doi cua tia mb lay diem d sao cho md =mb .tren tia doi cua tia cn lay diem e sao cho ne=nc.cminh d ,a ,e thang hang
Tam giac ABC vuong tai A, phan giac BD. Qua D ke d.thang vuong goc voi BC tai E.
a) CM: tam giac BAD = tam giac BED
b) BD la trung truc cua AE
c) AD <DC
d) tren tia doi AB lay diem F sao cho AF =CE. CM: ba diem E, D, F thang hang
