cho tam giac ABC co goc BAC lon hon hoac bang 60 do
C/m : AB+AC < 2BC
cho tam giac ABC, goc ABC lon hon 60 do. cmr AB+AC<=2BC
2 LIKE CHO ai giai dc dau tien
cho tam giac ABC co AB be hon AC, AD laf tia phan giac cua goc BAC(D thuoc BC). Tren canh AC lay diem E sao cho AE=AB.C/m rang tam giac ABD=tam giac AED, CD lon hon DB
cho goc Xay = 60 do. B la mot diem tren tia Ax, C la mot diem tren tia Ay(B,C khac A). C/m AB+AC be hon hoac bang 2BC
cho tam giac abc co goc a nho hon 90 do cho tam giac abc co 2 doan thang ad vuong goc va bang ab,ae vuong goc va bang ac
a, cmr dc=be va dc vuong goc voi be
b, goi n la trung diem cua de.tren tia doi cua tia na lay m sao cho na=mn . chung minh ab=me va tam giac abc=tam giac ema
1 cho tam giac abc can a , goc a bang 40 do lay d khac phia b so voi ac thoa man goc cad bang 60 do goc cad bang 80 do chung minh bd vuong goc voi ac
2 cho tam giac abc vuong can a . d la diem bat ki tren ab. tren nua mat phang bo ab tu c ve tia bx sao cho goc abx bang 135 do. duong thang vuong goc voi dc ve tu d cat bx o e . chung minh tam giac dec vuong can
3 cho tam giac abc can b goc abc bang 80 do , i la diem trong tam giac sao cho goc iac bang 10 do, ica bang 30 do tinh goc abi
4 cho tam giac abc can a co goc a bang 100 do , bc =a, ac =b ve phia ngoai tam giac abc ve tam giac abd can d co goc adb bang 140 do tinh ch vi tam giac adb theo a,b
ve hinh gium minh voi , xin mn day
cho tam giac ABC co AB nho hon AC D la trung diem BC tren tia doi DA lay E sao cho DA=DE
chung minh rang
a) tam giac ABC= tam giac ECD
b)EC lon hon AC
c) goc DAB nho hon goc DAC
cho tam giac abc co goc a bang 60. tia phan giac goc b cat ac tai d, tia phan giac goc c cat ab tai e.cac tia phan giac do cat nhau tai i. chung minh id=ie
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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 co goc A lon hon 90 do. Ke DA vuong goc voi AB va DA=AB ( tia AD nam giua 2 tia AB,AC).Ke AE vuong goc voi AC va AE=AC ( tia AE nam giua 2 tia AB,AC). Ke AH vuong goc voi BC va keo dai cat De tai M. CM MD=ME