Cho tam giac ABC .Ke trung tuyen AM Tren tia doi cua tia MA lay diem E sao cho ME=MA
a,Chung minh tam giac AMB=tam giac ECM
b,Ke AH vuong goc voi BC. Ten tia doi cua tia HA lay diem D sao cho HD=HA.Chung minh :BCla tia phan giac cua goc ABD va BD=CE
c.Hai duong thang BD va CE cat nhau tai K. Chung minh :tam giac BCK can
cho tam giac abc can tai a goc a la gic tu,tren tia doi bc lay diem d tren tia doi cua tia cb lay diem e sao cho bd =ce .tren tia doi ca lay diem i sao cho ci=ca.a) cm tam giac abd=tam giac ice.b)chung minh ab+ac<ad+ae.c)tu d va e ke duong thang vuong goc voi bc cat ab,ai theo thu tu mn .cm bm=cn.d)chung minh chu vi tam giac abc<chu vi tam giac amn
cho tam giac ABC v uong tai A (AB < AC ) , ke AH vuong goc voi BC tai H . tren canh AC lay diem I sao cho AH =AI . qua I ke duong thang vuong goc voi A C , cat BC tai D
a, CMR : tam giac AHD = tam giac AID va` AD la tia phan giac cua ∠HAC
b, tia ID cat tia AH tai M . CMR △MCD can
c, go.i N la` trung diem cua MC . CMR AN,MI,BC do^`ng quy
cho tam giac abc,ab=ac tren canh bc lay diem m.tren tia doi cua tia cb lay diem n sao cho bm=cn.tu m,n ke cac duong thang vuong goc voi bc cat ab,ac lan luot tai d,e
a) c/m DM=CN
b)DE cat bc tai i .chung minh i laf trung diem cua mn
Cho tam giac A,B,C vuong tai A ( AB nhỏ hơn AC ) . Kẻ AH vuông tại BC, H thuoc BC. Tren tia doi lay diem M sao cho HM = HA
A ) Chung minh : ∆ABH = ∆ MBH
B) Goi I la trung diem cua BC, qua C ke duong thang vuong tai AC, duong thang nay cat tia AI ở D . CM: AB=CD
C) Chung minh : BC // DM
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 can tai A.aTren canh BC lay diem d(D khac BC).Tren tia doi cua tia CB,lay diem E sao cho CE = BD. Duong vuong goc voi BC ke tu D cat BA tai M.Duong vuong goc voi BC ke tu E cat tia AC tai N.MN cat BC tai I
CMR : DM =ENCho \(\Delta ABC\)can tai A. Tu B ke duong vuong goc AB, tu C ke duong vuong goc voi AC.Hai duong thang cat nhau tai D. Chung minh rang
a, AD la phan giac cua goc BAC
b, Tren tia doi cua tia BD lay diem E, tren tia doi cua tia CD lay diem F sao cho CF= BE. chung minh AE= AF
c, Chung minh EF song song voi BC
CHO TAM GAIC ABC VUONG TAI A, CO AB = 3CM, AC=4CM.GOI AM LA DUONG TRUNG TUYEN, TREN TIA DOI CUA TIA MA LAY DIEM D SAO CHO AM=MD
A) TINH DO DAI CANH BC
B) CHUNG MINH AB=CD, AB//CD
C) CHUNG MINH GOC BAM>GOC CAM
D) GOI H LA TRUNG DIEM CUA BM, TREN DUONG THANG AH LAY DIEM E SAO CHO AH=HE, CE CAT AD TAI F. CHUNG MINH F LA TRUNG DIEM CUA CE