cho h.thang ABCD(AB//CD) va AB>DC va 2 duong cheo AC,DB vuong goc.Tren AB lay M sao cho AM co do dai bang d.t/b cua h.thang
C/m CA la tia p/giac goc MCD
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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 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 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
a)Xét ΔABM vuông và ΔACM vuông có:
AM chung
AB=AC
=> ΔABM = ΔACM
=> BAM = CAM ( 2 góc t.ư)
=> AM là p/g của góc BAC
cho tam giac ABC co AB bang AC,I la trung diem cua BC lay M thuoc AB ,N thuoc AC sao cho AM bang AN. CMR
Tam giac ANB bang tam giac AMC ,BN bang CMGoi H la giao diem cua CM va BN. CMR tam giac MAB bang NHCAI la phan giac cua BAC, AI la duong trung truc cua BCTren tia doi cua tia CA lay diem D sao cho AB bang CD ... Ke DE vuong goc vs BC, AE song song vs ID , AE bang ID
Cho tam giac ABC can tai A co AD la duong trung tuyen
a)Chung minh tam giac ABD= tam gaic ACD va AD vuong goc voi BC
b)Cho AB=10cm,BC=16cm. Tinh do dai AD va so sanh cac goc cua tam giac ABC.
c) Ve duong trung tuyen CF cua tam giac ABC cat AD tai M. Tinh do dai AM.
d) Ve DH vuong goc AC tai H, tren canh AC va canh DC lan luot lay hai diem E,K sao cho AE=AD va DK=DH. Chung minh: EK vuong goc voi BC
A,
xét \(\Delta ABD\)và \(\Delta ACD\)
CÓ \(\hept{\begin{cases}AB=AC\\chungAD\\BD=DC\end{cases}}\)
SUY RA \(\Delta ABD\)=\(\Delta ACD\) (C.C.C) (1)
=> \(\widehat{BDA}\)=\(\widehat{CDA}\)
MÀ \(\widehat{BDA}\)+\(\widehat{CDA}\)=180
=> \(\widehat{BDA}\)=\(\widehat{CDA}\)=90
B, (1) => BC=DC=1/2 BC=8
ÁP DỤNG ĐỊNH LÍ PITAGO TA CÓ
\(AB^2=AD^2+BD^2\)
=> AD^2=36
=>AD=6
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cho tam giac ABC co BC=4cm. tren tia doi cua tia BC lay diem D sao cho BD=2cm/ a, tinh do dai CD; b,goi M la chung diem cua CD.tinh do dai BM;c,biet goc DAC bang 112 do .Ãxtia phan giac cua goc BAC va goc BAD. tinh so do goc xAy;d, tren nua mat phang bo la duong thang AC co chua diem D neu ve them n tia goc A phan biet khong trung voi cac tia ÂC,Ã,AB,Ay,AD thi co tat ca bao nhieu goc dinh A va Ay thu tu la
cho tam giac ABC co goc A<90 do ve ra ngoaitam giac do hai doan thang AD vuong goc va bang AB, AE vuong goc va bang AC
a, chung minh DC vuong goc va bang BE
b, goi N la trung diem cua DE.Tren tia doi cua NA lay M sao cho NA=NM
chung minh AB=ME va tam giac ABC=tam giac EMA
c, chung minh MA vuong goc voi BC
giup mk cau c thoi cung dc mk dg can gap nha
1. cho tam giac ABC can tai A, ve diem M, Nbat ki tren duong trung truc ca doan thang BC.CM:a,tam giac MBCcan tai Mb, MNCMNB2.cho tam giac ABC cao M la trung diem cua canh BC. qua B ke duong thang Bx AC, qua C ke Cy AB. giao diem cua Cy, Bx la D. CM: A, D, M thang hang.3. do dai 2 canh goc vuong cua mot tam giac vuong ti le voi 7 va 24. chu vi tam giac bang 112. tinh do dai canh huyen.4.cho tam giac ABC can tai A, canh day nho hon canh ben. duong trung truc cua AC cat BC tai M. tren tia doi cu...
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1. cho tam giac ABC can tai A, ve diem M, Nbat ki tren duong trung truc ca doan thang BC.CM:
a,tam giac MBCcan tai M
b, MNC=MNB
2.cho tam giac ABC cao M la trung diem cua canh BC. qua B ke duong thang Bx \\ AC, qua C ke Cy \\ AB. giao diem cua Cy, Bx la D. CM: A, D, M thang hang.
3. do dai 2 canh goc vuong cua mot tam giac vuong ti le voi 7 va 24. chu vi tam giac bang 112. tinh do dai canh huyen.
4.cho tam giac ABC can tai A, canh day nho hon canh ben. duong trung truc cua AC cat BC tai M. tren tia doi cua AM lay N \ AN = BM.
a, CM: 2 goc AMC va BAC bang nhau
b, CM: CM = CN
c, de CM vuong voi CN hi tam giac ABC phai co them dieu kien gi?
5. cho tam giac ABC deu. tren tia doi cua tia phan giac goc BAC lay D \ AD = AB. tinh cac goc cua tam giac DBC.
1)cho tam giac abc co goc b=goc c.goi i la trung diem cua canh bc.tren canh ab laydiem d,tren tia di lay diem e sao cho i la trung diem de.cm:
a,bd=ce;
b,cb la tia phan giac cua goc ace
cho tam giac ABC co goc A=90 do va AB=AC.Tren canh AB,AC lay tuong ung 2 diem D va E sao choAD=AE.Tu A va D ke duong vuong goc voi BE cat BC tai M va N.Tia ND cat CA o I.CM:
a,A la trung diem cua CI.
b,CM=MN