cho tam giac ABC can tai A co A < 90 do, duong vuong goc voi AB tai B va duong thang vuong goc voi AC tai C va chung cat nhau tai M.
a, c/m tgABM = tgACM, AM la phan giac cua goc BAC
b, Qua M ve duong thang song song voi AC, duong thang nay cat AB o D. Tren tia doi cua tia CA lay diem E sao cho CE = DB, c/m tgDBM = tgECM
c, BC cat DM tai F. c/m DF = CE
Cho tam giac ABC co goc A = 60 do . Cac duong phan giac BD va CE cat nhau tai I . Tren canh BC lay M sao cho BM = BE . a) Chung minh tam giac MID can
b) ve duong thang vuong goc voi BI tai B va vuong goc voi CI tai C , chung cat nhau o K . CMR : 3 diem A,I,K thang hang
cho tam giac abc can tai a.tren duong thang vuong goc voi ac tai c lay diem d sao cho hai diem b,d nam khac phia doi voi duong thang ac.goi k la giao diem cua duong thang qua b vuong goc voi ab va duong thang qua trung diem m cua cd vuong goc voi ad.c/m kb=kd
Cho tam giac ABC co A=75, B=35. AD la tia phan giac cua goc A. Qua A ke duong vuong goc voi AD duong thang nay cat uong thang BC tai E. Tren nua mat phang bo AE cung phia voi C ve tia Ax sao cho AEC=EAx. Tia Ax cat ED tai M.
a) Chung minh: ME=MD
b) Chung minh: BC= chu vi tam giac ABC
c) Tu M; N ta ke cac duong thang lan luot vuong goc voi Ae; AM. Chung cat nhau tai O. Duong thang OC cat AE tai N va AD tai K.Chung minh MN vuong goc voi NK
cho 2 duong thang xy//mn ,duong thang A cat 2 duong thang xy va mn lan luot tai A va B. ke tia phan giac cua foc xAB va phan giac cua goc ABM chung cat nhau tai C. Ke tia phan giac cua BAI va tia phan giac cua ABN chung cat nhau tai D.chung minh: a)AC vuong goc voi AD, BD vuong goc voi BC
Cho tam giac ABC can tai A.Tren duong thang vuong goc voi AC tai C lay diem D sao cho hai diem B,D nam khac phia doi voi duong thang AC.Goi K la giao diem cua duong thang qua B vuong goc voi AB va duong thang qua trung diem M cua CD vuong goc voi AD.C/m KB=KD
Cho tam giac ABC can tai A.Tren duong thang vuong goc voi AC tai C lay diem D sao cho hai diem B,D nam khac phia doi voi duong thang AC.Goi K la giao diem cua duong thang qua B vuong goc voi AB va duong thang qua trung diem M cua CD vuong goc voi AD.C/m KB=KD
Cho tam giac ABC can tai A.Tren duong thang vuong goc voi AC tai C lay diem D sao cho hai diem B,D nam khac phia doi voi duong thang AC.Goi K la giao diem cua duong thang qua B vuong goc voi AB va duong thang qua trung diem M cua CD vuong goc voi AD.C/m KB=KD
Cho tam giac ABC can tai A.Tren duong thang vuong goc voi AC tai C lay diem D sao cho hai diem B,D nam khac phia doi voi duong thang AC.Goi K la giao diem cua duong thang qua B vuong goc voi AB va duong thang qua trung diem M cua CD vuong goc voi AD.C/m KB=KD