Cho tam giac ABC. Mot duong thang song song voi BC cat cac canh AB, AC theo thu tu o D va E. Goi G la mot diem thuoc canh BC. Tinh dien tich tu giac ADGE biet dien tich tam giac ABC bang 16cm, dien tich tam giac ADE bang 9 cm
cho tam giac abc diem m thuoc bc .qua m ke duong thang song song voi ab cat ac tai d. qua m ke duong thang song song voi ac cat ab o e
a adme la hinh gi
b tim vi tri cua m tren bc de tu giac adme la hinh thoi
c,tim dieu kien cua tam giac abc de tu giac adme la hinh chu nhat
cho hinh chu nhat ABCD co AD= 6cm, AB=8cm, hai duong cheo AC va BD cat nhau tai O. Qua D ke duong thang d vuong goc voi BD, d cat BC tai E.
a) Chung Minh: Tam giac BDC dong dang voi tam giac DCE.
b) Ke CH vuong goc voi DE tai H. CMR: DC.DC=CH.DB
c) goi K la giao diem cua OE va HC. Chung minh K la Trung diem cua HC va tinh ti so dien tich tam giac EHC vatam giac EDB.
d) Chung Minh Rang: Ba duong thang OE, CD, BH Dong Quy.
( Ve Hinh Nhe)
cho tam giac abc(ac>ab)ad la duong phan giac trong. Qua c ke tia cx sao cho cb nam giua ca la e. Duong thang di qua d song song voi ce cat be o i.a)CM tam giac adb dong dang tam giac cde va ab/ac=bi/ie. b) CM tam giac bde dong dang tam giac adc. c)CM ab•ac-bd•dc=ac^2
cho tam giac abc, trung tuyen am. gio g la trong tam cua tam giac abc. qua g ke cac duong thang song song voi ab va ac, cat bc theo thu tu tai d va e. a, tinh va so sanh cac ti so bd/bm va ce/cm tu do suy ra bd=ce. b, chung minh bd=de=ce
cho tam giac ABC vuong tai A,D la diem thuoc canh BC duong thang qua D song song AC cat AB tai E,duong thang qua D song song AB cat AC tai f
a)chung minh AD=EF
b)xac dinh vi tri D de dien tich AEDF=\(\frac{1}{2}\)dien tich tam giac ABC
ai lam duoc minh tick cho khoi ve hinh
cho tam giac ABC có AB=12cm,AC=20cm,BC=28cm.Đường phân giac góc A cắt BC tại D qua D kẻ DE//AB (E thuộc AC).
a) tính BD,DC,DE
b) biết diện tích tam giac ABC là S tính diện tích các tam giac ABD,ADE,DCE.
AI NHANH MIK TICK CHO NHA ^^
Cau 1: Cho tam giac ABC cuong tai A, AB=8cm; AC=15cm. Ve duong cao AH
a) chung minh AB^2= BH. BC
b) Tinh BH, CH, AH, BC
c) Ve phan giac AD cua tam giac ABC. Chung minh H nam giua B va D
d) Tinh ti so dien tich D HAC va D A.BC
Cau 2: Cho tam giac ABC vuong tai A, AB=5cm; Ac=12cm, ve duong cao AH va duong phan giac AD.
a) Tinh BC, BD
b) Chung minh D ACH: D ABC; tinh AH
c) Qua B ke duong thang vuong goc voi AB cat tia AD tai K. Chung minh AB.AD =AC. KD
.Cau 3: Cho tam giac ABC vuong A co AB = 5cm; AC=12cm. Ve dcao AH va pgiac AD cua goc BAC
a) Tih BC; BD
b) Chung minh D HAC : D ABC
c) Qua B ke duong vgoc voi BA cat AD tai k. Chung minh AB.AD= AC.KD
Cho tam giac ABC co AB=12cm,AC=20cm va BC=28cm.Duong phan giac cua goc A cat BC tai D
a) tinh BD ,DC
b) ve DE song song voi BC tinh DE
theo mk thay dau bai nay hoi sai ban nao thay vay thi noi mk bit nha. neu giai dk ve hinh cho mk nha