a: Sửa đề: CM MN//BD
Xét ΔABD có AM/AB=AN/AD
nên MN//BD
b: Xét ΔAHM vuông tại H và ΔDHA vuông tại H có
\(\widehat{HAM}=\widehat{HDA}\)
DO đó: ΔAHM\(\sim\)ΔDHA
Giup mink !
Bai 1: Cho tam giac ABC co 3 goc nhon . Cac duong cao lan luot la AD,BE,CF cat nhau tai H
a.C/m tam giac AEF dong dang tam giac ABC
b.C/m tam giac AEF dong dang tam giac DBF
Bai 2: Cho tam giac ABC vuong tai A , AB=9 cm,AC=6 cm , duong cao AH , duong phan giac BD. Ke DE vuong goc BC (E thuoc BC), duong thang DE cat duong thang AB tai F .
a.Tinh BC,AH?
b.Chung minh tam giac EBF dong dang tam giac EDC
c.Goi I la giao diem cua AH va BD. Chung minh AB.BI=BH.BD
d.C/m BD vuong goc CF
e.Tinh ti so dien tich cua 2 tam giac ABC va tam giac BCD
1. Cho hinh binh hanh ABCD. Ke AH vuong goc CD, AK vuong goc BC
a. chung minh tam giac AHD dong dang tam giac AKB
b. biet AB = 12, AD = 8, CK = 3. Tinh AK va AH
2. Cho tam giac ABC (AB < AC). Duong cao BH va CK cat nhau tai I
a. chung minh tam giac IKB dong dang tam giac IHC, tam giac IHC dong dang tam giac AKC
b. chung minh KI*KC = KA*KB
AC*BK + BI*CK
cho tam giac MNQ vuong tai M ke ME vuong goc voi MQ (E thuoc NQ)
A)chung minh :tam giac EMQ dong dang voi tam giac MNQ
B) chung minh :tam giac EMQ2=EQ,NQ
1 Cho tam giac ABC vuong tai A ,co AH la duong cao
a,C/m AB^2=BH.BC
b,tia phan giac cua goc B cut AH tai D va cut AC tai E.C/minh tam giac ADB dong dang tam gic CED
C,tam giac ADE la tam giac gi Vi sao
2,Cho tam giac Abc vuong taij A , AH la duong cao
a,c/m tam giac Hba dong dang tam giac ABC
=>AB^2=BH.BC
b,Tia phan giac cua goc abc CUT AH taij E cut AC tai D C/minh tam giac ABE dong dang tam giac CBD
suy ra AD=AE
c,C/m AD^2=EH.DC
Cho tam giac ABC vuong tai A ( AB<AC) ve duong cao AH ( H thuoc BC)
A) cm tam giac ABH dong dang tam giac CBA suy ra Ab binh=BH.BC
cho hinh chu nhat ABCD ,ve BH vuong goc vs AC (H thuoc AC) .Goi M,N lan luot la trung dm cua doan AH va CD.CMR:BM vuong goc vs MN
cho tam giac abc ke ah vuong bc,ad la tia pg goc a,am la trung tuyen hoi h,d,m diem nao nam giua 2 diem con lai vi sao
cho tam giac ABC vuong o A co AB=15cm va AC=12cm duong trung tuyen AM
Tinh BC va AM
Ve Ax vuong goc AM va By vuong goc BA.Tia Ax va By cat nhau tai E.Ve BF vuong goc AE tai F.CM :goc ABF =gocBAMva \(\Delta ABC\) dong dang \(\Delta FBE\)
\(AM\cap BE=\left\{D\right\},MF\cap BE=\left\{I\right\}.CM:ABClaHCN\),I la trung diem cua BF
\(ME\cap AB=\left\{K\right\}.\)CM: D,F,K thang hang
cho tam giac abc co 3 goc nhon (ab<ac), bd va ce la 2 duong cao cat nhau tai h
a) chung minh tam giac abd dong dang voi ace
b) chung minh hb.hd=hc.he
c) ve dm vuong goc voi bc tai m, cho bc=10cm, bm=3,6cm, tinh dm
