cho hinh vuong ABCD. Qua A ve hai duong thang vuong goc voi nhau lan luot cat BC tai P va R, cat Cd tai Q va S.
a, chung minh tam giac AQR va tam giac APS la cac tam giac can
b, QR cat PS tai H; M,N la trung diem cua QR va PS. chung minh tu giac AMHN la hinh chu nhat
c, chung minh P la truc tam
d, chung minh MN la duong trung truc cua AC
e, chung minh bon diem M, B,N,D thang han
cho hinh vuong abcd, ac cat bd tai e, duong thnag qua a cat bc tai m , cat duong thang cd tai n,em cat bn tai k. chung minh ck vuong goc voi bn
cho hinh vuong abcd co ac cat bd tai o.m la diem bat ki thuoc canh ad(m khac d,a).tia bm cat duong thang cd tai n,om cat an tai i.C/m di vuong goc voi an
De bai : Cho tam giac ABC co AB=9 cm,BC=12 cm,BC=15 cm
a,C/m tam giac ABC vuong
b,Duong phan giac cua goc B cat AC tai D . Tinh AD,DC
c,Duong cao AH cat BD tai I. Chung minh IH.BD=IA.IB
d,Chung minh tam giac AID can
cho tam giac ABC vuong tai A co AB=9cm BC=15cm tren tia doi cua tia AB lay diem D sao cho A la trung diem cua doan thang AB
a, tinh do dai canh AC va ss cac goc cua tam giac ABC
b, cm tam giac BCD can
c, goi E la trung diem cua canh CD ,BE cat AC o I .cm DI ik qua trung diem cua canh BC
(ve hinh )
cho hinh vuong abcd.tren canh bc lay mot dien tuy y .duong thang vuong goc am tại m cat cd tai e và ab tai f.cmr ma=fe
bai 3 ; cho tam giac abc . tren canh ab lay diem m , tren canh ac lay diem n sao cho bm = cn . goi i la trung giem doan bn , goi k la trung diem doan cm , duong thang ik cat ab tai p , cat ac tai q . chung minh rang tam giac apq la tam giac can .
cho tam giac abc vuong tai a, duong cao ah
a. chung minh tam giac hba dong dang voi tam giac abc
b. chung minh ah^2 =hb* hc
c. tia phan giac cua goc ahc cat ac tai d . chung minh \(\frac{hb}{hc}\)=\(\frac{ad^2}{dc^2}\)
Cho tam giac ABC co 3 duong trung tuyen AM,BN,CP.Qua N ke duong thang song song voi PC cat BC tai F , duong thang qua F song song voi PN va duong thang qua B song song voi CP cat nhau tai D . Goi G la trong tam cua tam giac ABC .CMR : \(S_{ABG}=S_{GBC}=S_{GCA}\)
