cho tam giac ABC co goc BAC lon hon hoac bang 60 do

  C/m : AB+AC < 2BC

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 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

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 tam 2 ABC vuong can tai AC lon hon AB ve duong phan giac AB ke DK vuong goc AC tai K; a, chung minh tam giac ADK vuong can ,b chung minh AK <DC ,chung minh BD <AB ,d qua D ke duong thang vuong goc voi BD va cat canh AC o E tinh so do goc BCE

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

Moi nguoi oi giup em voi khan cap qua mai em phai nop bai roi

Cau mot Cho tamgiac abc ab < ac cac tia phan giac cua goc b va goc c cat nhau tai o . hayso sanh ba canh

cua tam giac obc

Cau hai cho tam abc canh ab nho nhat chung minh rang goc a cong goc b lon hon 120 do

cho tam giac ABC co goc A lon hon 90 độ. Chứng minh AB²+AC²<BC²

Bai 1: Cho tam giac ABC nhon, duong cao BD, CE
a) CMR: tam giac ABD dong dang voi tam giac ACE
b) CMR: goc BED + goc BCD = 180 do
c) Cho goc BAC = 60 do; dien tich tam giac AED = 90 do . Tinh tam giac ABC