a: Xét ΔBNC và ΔCMB có
NB=MC
\(\widehat{NBC}=\widehat{MCB}\)
BC chung
Do đó: ΔBNC=ΔCMB
b: Xét ΔKBC có \(\widehat{KBC}=\widehat{KCB}\)
nên ΔKBC cân tại K
1.cho tam giac ABC can tai dinh A, trung truc cua canh AC cat CB tai diem D (D nam ngoai doan BC). tren tia doi cua tia AD lay diem E sao cho AE= BD. chung minh tam giac DEC can.( goi y can chung minh CD = CE)
2. cho tam giac ABC co AB < AC, lay diem E tren canh CA sao cho CE=BA, cac duong trung truc cua cac doan thang BE va CA cat nhau tai I
a)chung minh tam giac AIB = tam giac CIE
b)chung minh AI la tia phan giac cua goc BAC
cho tam giac ABC vuong tai A(AB<AC). Tia phan giac cua goc B cat AC o E. TRen BC lay diem d sao cho BD=BA. Duong thang DE at duong thang AB tai F.
a, CM ED vuong gic voi BC
b,CMR tam giac BCF can tai b
c, Goi H la giao diem cua BE va FC. TINH BC biet BH=8cm, FC=12cm
d, CM AD song song voi FC
Cho tam giac ABC can tai C . Ve CH vuong AB tai H
1 ) Cm : H la trung diem cua AB
2 ) Tia phan giac cua goc CAB cat CH tai D . Cm : tam giac ADB la tam giac can
3 ) Tren canh AC lay K sao cho AK = AH . Cm : DK vuong AC
4 ) Cho AD=5cm , AB = 8 cm . Tinh DH
5 ) Tim dieu kien cua tam giac ABC de 3 diem B , D , K thang hang
DANG CAN GAP !
cho ΔABC vuong tai A, co C=30 . BD la tia phan giac cua ABC. ke DH vuong goc voi BC. tia BA va HD cat nhau tai K
a, cm Dla trong tam cua ΔBKC
bAD+AK>\(\dfrac{kc}{2}\)
cho tam giac abc vuong tai a ,duong trung tuyen am.tren tia doi cua tia ma lay d sao cho md=ma.tinh goc abd
bai 1: cho tam giac ABC deu, ke AH vuong goc voi BC (H thuoc BC). Tia phan giac cua goc ABC cat AH tai E. Ve EK vuong goc voi AB 9 K thuoc AB). Lay I la trung diem cua AC. CMR
a, tam giac EHB = tam giac EKB
b, tam giac BHK deu
c, tam giac AKH can
d, ba diem B,E,I thang hang
MK DANG CUC KI CAN GAP HELP
Cho tam giac ABC can tai A, duong trung tuyen AM. Cho biet AB= 13cm, BC= 10cm.
a. Tinh do dai AM
b. Tren AM lay diem M sao cho GM=1/3AM. Tia BG cat AC tai N. Chung minh: NA=NC
c. Tinh do dai BN
d. Tia CG cat Ab tai L. Chung minh rang LN//BC.
May tinh cua minh ko the viet co dau nen cac ban thong cam. Giai jup minh vs a, minh ko hiu. Thanks a lot!
Cho tam giac ABC (AB>AC).M la trung diem cua BC.Duong thang qua M va vuong goc voi tia phan giac cua goc A tai H cat AB,AC lan luot tai E,F
a,CM H la trung diem EF va EF^2/4+AH^2=AE^2=AF^2
b,CM goc ACB=2*goc BME+ goc ABC
c, CM BE=CF
help me
Bài 1. Cho goc xOy , co Ot la tia phan giac. Lay diem A tren tia OOx, diem B tren tia OOy sao cho OA=OB. ve doan thang AB cat Ot tai M. Chung minh
A. Tam giac OAM=▲OBM
b. AM=BM;OM vuong tai AB
C. OM la duong trung truc cua AB
D. tren tia Ot lay diem N. Chung minh NA=NB
