dùng hệ thức lượng giác trong tam giác vuông
\(tan\widehat{ABC}=\frac{AC}{AB}\Rightarrow AC=tan\widehat{ABC}.AB=tan30^0.3=\frac{\sqrt{3}}{3}.3=\sqrt{3}\left(cm\right)\)
\(sin\widehat{ABC}=\frac{AC}{BC}\Rightarrow BC=\frac{AC}{sin\widehat{ABC}}=\frac{\sqrt{3}}{sin30^0}=\frac{\sqrt{3}}{\frac{1}{2}}=2\sqrt{3}\left(cm\right)\)
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
Chao cac gia su va cac ban.Minh co 1bai toan chua lam duoc.Nhu lan truoc,minh da dat cau hoi ve hinh hoc.Lan nay minh xin dat mot cau nua,mong moi nguoi giup minh bai toan nay :
Cho tam giac ABC vuong tai A,co goc B =60 do.
a, Tinh so do goc C va so sanh do dai 3canh cua tam giac ABC
b,Ve BD la tia phan giac cua goc ABC(D thuoc AC).Qua D ve DK vuong goc voi BC(K thuoc BC) .Chung minh:tam giac BAD=tam giac BKD
c,C/minh :tam giac BDC can va K la trung diem BC
d,Tia KD cat BA tai I.Tinh do dai canh ID biet AB=3cm(lam tron ket qua den chu so thap phan thu nhat).
Neu ai, gia su co the tra loi duoc cau hoi nay thi xin nhan tin lai cho minh a.Minh xin cam on nhieuuuuuuuu(ve hinh nua nhe! )
cho tam giac ABC vuong tai a, co B=60 va AB=5cm .tia phan giac cua goc B cat AC tai D .Ke de vuong goc voi AC tai E
1/ chứng minh tam giác ABD= tam giác EBD
2/chung minh tam giac ABE la tam giac deu
3/tinh do dai canh BC
cho tam giac ABC vuong tai A co goc B=30 tren tia doi cua tia AC lay D sao cho AC=AD do dai can AC=8. Tinh BD
cho tam giac abc deu co canh 10cm.tu A dung tia Ay vuong goc voi AB cat BC tai M.
a)CM:tam giac acm can
b)ke AH vuong goc BC , lay I thuoc AH . Biet AB<AM.CM IB < IM
c)ke CN vuong goc AM , noi HN, CM tam giac AHN deu
d)tinh do dai doan HN
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cac ban chi can lam cau C ho minh thoi nhe :) thanks
cho tam giac ABC can co AB = AC = 5cm ; BC = 8cm . Ke AB vuong goc voi BC tai H
a, chung minh HB = HC va gocBAH = gocCAH
b, tinh do dai AH
c, ke HD vuong goc voi AB tai D. HE vuong goc voi AC tai E
chung minh tam giac HDE la tam giac can
cho tam giac abc vuong tai a biet ab=6cm ac=8cm tinh do dai bc va so sanh cac goc ABC va goc ACB phan giac goc ABC cat AC tai M ve MN vuong goc voi BC tai N chung minh AB=BN tia BA va NM cat nhau tai I chung minh IC//AN
cho tam giac ABC, ke AH vuong goc voi BC. Biet AB=5cm, BH=3cm, BC=8 cm. tinh do dai cac canh AH,HC,AC?
giup mk vs
Cho tam giac ABC co AB =6cm , AC=8cm, BC =10cm .
a) Chung minh tam giac ABC vuong .
b) Ke AH vuong goc voi BC . Biet AH=4,8cm . Tinh do dai cac doan BH,CH .