ho tam giac abc . Tren nua mat phang co bo la duong thang AC chua diem B ve tia AD//BC .Tren nua mat phang doi voi nua tren ve tia AE//BC.Tren nua mat phang doi voi nua tren ve tia AE//BC a cmr 3 diem A,D,E thang hang ,b Tinh tong cac goc trong cua tam giac?

cho tam giac abc,m la trung diem cua bc.tren nua mp bo bc khong chua diem a ve tia Cx sao cho Cx//AB.tren tia Cx lay diem d sao cho cd=ab.CMR

a,MA=MD

b,3 diem A,M,D thang hang

cho tam giac ABC co AB=AC AB>BC goi M la trung diem cua BC a) CMR tam giac ABC=tam giac ACM va AM la duong trung truc cua BC b)tren tia doi cua MA lay D sao cho MD=MA. CM :AB//CD c)tren nua mat phang co bo chua AC ko chua B ke Ax vuong voi AM.tren Ax lay E sao cho AE=BC.CMR:3 diem D,C,E thang hang

Cho tam giac ABC vuong can tai A, D la mot diem bat ki tren canh AB. Tren nua mp bo AB co chua diem C, ve tia?

mat phang bo AB co chua diem C, ve tia Bx de goc ABx=135 do. Duong thang vuong goc vs Dc ve tu D cat tia Bx tai E. Chung minh tam giac DEC can

giups mk

Cho tam giac ABC .goc A {90* . tren nua mat phang bo AB ko chua diem C, ve Ax vuomg goc voi AB, tren do lay D sao choAD=AB .tren nua mat phang bo AC, ko chua diem B ,ve Ay tren do lay E sao cho AE=AC a cmr BE=CD b duong thang AC va ED co vuong goc voi nhau ko?

Cho tam giac ABC vuong can tai A, D la mot diem bat ki tren canh AB. Tren nua mp bo AB co chua diem C, ve tia  Bx de goc ABx=135 do. Duong thang vuong goc vs Dc ve tu D cat tia Bx tai E. Chung minh tam giac DEC can

Cho tam giác ABC co A nho hopn 90 do . Tren nua mat phang bo AB khong chua diem C, ve doan thnag AD vuong goc Ab va AD=AB.Tran nua mat phang bo ac khong chua B, ve doan thnag Ae vuong goc AC va ae= AC. Goi F la trung diem cua BC. Chung minh 

a. D,A,E khong thang hang va  BA khong vuong goc voi DE

Tren duong thag a lay ba diem A,O,A'(O nam giua A va A').Ve tia OB sao cho  AOB=45°,tren nua mat phang co bo la duong thang a khong chua tia OB ve tia OC sao cho AOC=90°

a.Goi OB' la tia phan giac cua goc A'OC.Chung minh rang:hai goc AOB va A'OB' la hai goc doi dinh

b,Tren nua mat phang co bo la duong thang a chua tia OB ve tia OD sao cho BOD=90°.Tinh so do goc A'OB'

cho tam giac ABC co goc a nhon M la trung diem cua BC tren tia doi cua tia MA lay diem D sao cho MA=MD chung minh BAM=CDM chung minh AC=AD tren nua mat phang Bo AB ko chua C ve tia Ax vuong goc AB tren nua mat phang bo AC ko chua B ve tia Ay vuong goc AC tren tia Ax lay Diem P sao cho AP=AB tren tia Ay lay diem Q sao cho AQ=AC chung minh tam giac ABQ= tam giac APC goi giao diem cua DA va PQ la K chung minh AK vuong goc PQ