Xét ΔABC có: AB < AC
\(\Rightarrow\widehat{ABC}>\widehat{ACB}\)(định lí)
Xét ΔABH vuông tại H:
\(\widehat{ABH}+\widehat{BAH}=90^o\)(phụ nhau)
\(\Rightarrow\widehat{ABH}=90^o-\widehat{BAH}=90^o-60^o=30^o\)
cho tam giac ABC co goc ACB bang 60 do .
a) ve tam giac ABC
b) hai tia phan giac cua goc ABC va ACB cat nhau tai I . Qua I ve duong thang song song Bc , duong thang nay cat cac duong thang AB va AC tai D v E .Tinh so do goc ACI va goc CIE
c) So sanh 2 goc DIB va ABI
d) Qua A ke AH vuong goc voi BC tai H , qua C ke CK vuong goc voi DE tai K .Giai thic vi sao AH song song voi CK
e) tinh so do goc CAH
GIAI NHANH GIUM MINH NHA!!!MINH DANG CAN GAP ...
cho tam giac abc vuong tai a,goc b co so do=60 do.ve ah vuong voi bc
a)so sanh ab va ac ; bh va hc
b)lay d thuoc tia doi cua tia ha sao cho hd=ha .chung minh rang hai tam giac ahc va dhc bang nhau
c)tinh so do goc bdc
Cho ∆ ABC vuong tai A, ke duong phan giac BK cua goc B. Duong tang di qua A va vuong goc voi BK cat BC tai H.
a, chung minh BA=BH
b, chung minh ∆BHK la ∆ vuong
So sanh AK va KC
Gia su goc C = 30°. Tam giac ABH la tam giac gi? Vi sao?
Bai 2 cho ∆ABC can tai A (AB=AC), BH vuong goc voi AC. Chung minh goc BAC =2 goc CBH.
cho tam giac ABC co goc B = 45 độ goc C bang 30 do duong cao AH M la diem tren AC sao cho AM = AH a, chung minh M la trung diem cua AC,
b, tinh so do goc AMB :
c, goi D la giao diem cua BM va phan giac goc ACB thi tam giac ABD la tam giac gi
cho tam giac ABC co AB<AC ,ke duong cao AH .so sanh goc BAH va goc HAC
cho tam giac ABC vuong tai A ( AB < AC ) tren canh BC lat diem K / AB = BK . Goi H la TD AK . Keo dai BH cat AC ai I
a neu goc ABC = 60 . tinh so do ACB
b cm 2 tam giac ABH = KBH . tu do suy ra HK vuong vs BI
c qua K ke duong thang song song AC , cat BH va AB lan luot N va D . cm KA la tia pg IKD
d ke AM vuong goc vs BC tai M . cm 3 diem A , N .M thang hang
cho tam giac ABC co goc ABC=30do va goc BAC=130do. goi Ax la tia doi cua tia AB, duong phan giac cua goc ABC cat phan giac cua goc CAx tai D. duong thang BA cat duong thang CD tai E. So sanh do dai AC va CE
Tam giac ABC nhon co AB < AC . Ke AH vuong goc voi BC tai H . Ve phia ngoai tam giac ABC ve doan thang BD vuong goc voi AB , BD = AB va CE vuong goc voi AC , CE = AC . Ke DM vuong goc voi duong thang BC tai M va EN vuong goc voi duong thang BC tai N
1, So sanh goc DBM voi goc BAH , goc ECN voi goc CAH
2, Chung minh : DM = BH va EN = CH
Giup mk vs:
Cho tam giac ABC vuong tai A. Duong phan giac cua goc B cat AC tai H. kE he VUONG GOC VS bc. Duong thang EH VA BA cat nhau tai I.
a, CM tam giac ABH = tam giac EBH
b,BH la duong trung truc cua AI
c, so sanh HA va HC
d, CM BH vuong goc vs IC.
GIUP MK VS.
