cho tam giac ABC va diem O bat ky trong tam giac cac tia AO,BO,CO cat BC,CA,AB tai P,Q,R.CMR ≥8

Cho tam giac ABC vuong tai A . tu 1 diem K bat ky thuoc canh BC ve KH vuong goc vs AC . tren tia doi cua tia HK lay I sao cho HI =HK

a,  chung minh AB song song voi HK

b, chung minh tam giac AKI can

c, chung minh goc BAK= gocAIK

d, chung minh tam giac AIC =tam giac AKC

Cho tam giac deu ABC co canh = 3cm, M la diem bat ki trong tam giac ABC. Qua M ke cac duong song song voi  AB, BC, CA, chung cat BC, CA, AB theo thu tu o A', B', C'. Ta co MA'+ MB'+ MC' =

giup minh cau nay voi : cho tam giac ABC vuong tai A voi cac duong phan giac trong BM va CN .chung minh bat dang thuc (MC+MA)(NB+NA)/MA.NA >= 3+2√2

Cho tam giac ABC, K la diem bat ki thuoc canh AC.CMR:KB+KC<AB+AC(dung bat dang thuc cua tam giac)

chung minh bat dang thuc 2(a^4+1) + (b^2 +1)^2>=2(ab+1)^2

a. tim mot cach chung minh khac cua bat dang thuc tam giac

b. cho tam giac MNP. goi I la trung diem cua doan thang MN. chung minh rang: PM + PN > 2 PI

Cho tam giac ABC,AB=AC,A' la diem bat ki tren canh AB.Duong phan giac goc A cat cạnh A'C tai M,cat canh BC tai N

a)chung minh CM=BM

b)Ve A'H vuong goc voi BC tai H.Chung minh goc A=2.BA'H

Cho tam giac ABC duong cao AD,H la truc tam cua tam giac .Lay M bat ki thuoc canh BC .Goi F,E la hinh chieu cua M tren AB,AC Goi I la trung diem cua AM 

a,Xac dinh dang cua tu giac

b,chung minh rang cac duong thang MH,ID,EF dong quy