cho tam giac ABC co AB=AC. goi H la trung diem cua canh BC . CMR
a/AH la tia phan giac cua goc BAC va AH vuong voi BC
b/tren tia doi cua tia HA lay diem K sao cho HK=AH.Chung minh rang CK//AB
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Cho tam giac ABC vuong tai A co goc B = 60° .Ve AH vuong goc voi BC tai H A/Tinh goc HAB B/Tren canh AC lay D sao cho AD=AH .Goi I la trung diem cua canh HD. C/M tam giac AHI= tam giac ADI . Tu do suy ra AI vuong goc voi HD C/Tia AI cat canh HC tai diem K .C/M tam giac AHK=tam giac ADK.Tu do suy ra AB//KD D/Tren tia doi cua tia HA lay E sao cho HE=AH.C/M H la trung diem cua BK va 3 diem D,E,K thang hang
a: \(\widehat{HAB}=90^0-60^0=30^0\)
b: Xét ΔAHI và ΔADI có
AH=AD
HI=DI
AI chung
Do đó: ΔAHI=ΔADI
Ta có: ΔAHD cân tại A
mà AI là đường trung tuyến
nên AI là đường cao
c: Xét ΔAHK và ΔADK có
AH=AD
\(\widehat{HAK}=\widehat{DAK}\)
AK chung
Do đó: ΔAHK=ΔADK
Suy ra: \(\widehat{AHK}=\widehat{ADK}=90^0\)
=>DK//AB
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bài 1: Cho tam giac ABC co AB AC. Goi H la trung diem cua BC. Tren tia doi cuatia BC lay diem M va tren tia doi cua tia CB lay diem N sao cho MB CN.a) Chung minh rang: AABH AACHb) Chung minh rang: AH la tia phan giac cua goc BACc) Chung minh rang: AH 1 BCd) Ching minh rang: AM ANe) Chung minh rang: H la trung diem cua MNTren nua mat phang bo MN khac phia voi A, lay diem E sao cho EM EN.Chung minh rang: A, H, E thang hang.bài 2: Chung minh rang: Trong mot tam giac vuong, canh doi dien voi g...
Đọc tiếp
bài 1: Cho tam giac ABC co AB = AC. Goi H la trung diem cua BC. Tren tia doi cua
tia BC lay diem M va tren tia doi cua tia CB lay diem N sao cho MB = CN.
a) Chung minh rang: AABH = AACH
b) Chung minh rang: AH la tia phan giac cua goc BAC
c) Chung minh rang: AH 1 BC
d) Ching minh rang: AM = AN
e) Chung minh rang: H la trung diem cua MN
Tren nua mat phang bo MN khac phia voi A, lay diem E sao cho EM = EN.
Chung minh rang: A, H, E thang hang.
bài 2: Chung minh rang: "Trong mot tam giac vuong, canh doi dien voi goc 30 do se bang
nua canh canh huyen"
mong trả lời nhanh
Cho tam giac ABC co AB= AC. Tia phan giac cua goc BAC cat BC tai D
CMR Tam giac ABD = tam giac ACD
Tren tia doi cua tia AD lay E sao cho AE=AD va tren tia doi cua tia AB lay F sao cho AF=AB CMR EF=BD
Goi H la trung diem cua FC. Cmr AH la tia phan giac cua goc CAF
CMR AH//BC
Giai giup minh som nhat, chi tiet nhat, minh cho 5 sao!!!!
cho tam giac[ABC vuong tai A, co goc B 60 do. ve AH vuong goc voi BC tai H. tren canh AC lay diemE sao cho AD AH. goiI la trung diem cua canh HD. tia AI cat canh HC tai diem K a) tinh ;so do goc HAB b) chung minh tam giac AHI tam giac DHI. tu do ;suy ra AI vuong goc HD c)chung minh AB // KD d)tren tia doi cua tia HA lay diem E sao cho HE AH. chung minh H la trung diem cua canh BC va ba diem D, K, E thang hang giup voi nha moi nguoi. minh can gap
Đọc tiếp
cho tam giac[ABC vuong tai A, co goc B = 60 do. ve AH vuong goc voi BC tai H. tren canh AC lay diemE sao cho AD= AH. goiI la trung diem cua canh HD. tia AI cat canh HC tai diem K
a) tinh ;so do goc HAB
b) chung minh tam giac AHI = tam giac DHI. tu do ;suy ra AI vuong goc HD
c)chung minh AB // KD
d)tren tia doi cua tia HA lay diem E sao cho HE = AH. chung minh H la trung diem cua canh BC va ba diem D, K, E thang hang
giup voi nha moi nguoi. minh can gap
Cho tam giac ABC can tai A co goc A=40 do.Tren canh AB lay diem D,tren tia doi cua tia CA lay diem E sao cho BD=CE.Ke DH va EK cung vuong goc voi duong thang BC.(H,K thuoc BC)
1.Tinh goc B,goc C cua tam giac ABC
2.CM :DH=EK
3.Goi M la trung diem cua HK,chung minh M la trung diem cua DE
bai 4:cho tam giac ABC co goc A90 do.Goi M la trung diem cua AC,tren tia Bm lay diem N sao cho M la trung diem cua doan BN.CMR:
a)CN vuong goc voi AC va CNAB
b)ANBC va AN song song voi BC
bai 4:cho tam giac ABC ke AH vuong goc voi BC(H thuoc BC)goi M la trung diem cua canh BC.Biet goc BAHgoc HAMgoc MAC.Tinh cac goc cua tam giac ABC
bai 6:cho tam giac ABC vuong tai A,phan giac BD.Tren canh BC lay diem H sao cho BHBA
a)CMR:DH vuong goc voi BC
b)BIET goc ADH120 do.Tinh goc ABD
Đọc tiếp
bai 4:cho tam giac ABC co goc A=90 do.Goi M la trung diem cua AC,tren tia Bm lay diem N sao cho M la trung diem cua doan BN.CMR:
a)CN vuong goc voi AC va CN=AB
b)AN=BC va AN song song voi BC
bai 4:cho tam giac ABC ke AH vuong goc voi BC(H thuoc BC)goi M la trung diem cua canh BC.Biet goc BAH=goc HAM=goc MAC.Tinh cac goc cua tam giac ABC
bai 6:cho tam giac ABC vuong tai A,phan giac BD.Tren canh BC lay diem H sao cho BH=BA
a)CMR:DH vuong goc voi BC
b)BIET goc ADH=120 do.Tinh goc ABD
Bài 6:
b) Theo câu a) ta có \(\Delta ABD=\Delta HBD.\)
=> \(\widehat{ADB}=\widehat{HDB}\) (2 góc tương ứng).
Ta có: \(\widehat{ADB}+\widehat{HDB}=\widehat{ADH}\left(gt\right)\)
=> \(\widehat{ADB}+\widehat{HDB}=120^0\)
Mà \(\widehat{ADB}=\widehat{HDB}\left(cmt\right)\)
=> \(2.\widehat{ADB}=120^0\)
=> \(\widehat{ADB}=120^0:2\)
=> \(\widehat{ADB}=60^0.\)
=> \(\widehat{ADB}=\widehat{HBD}=60^0\)
Xét \(\Delta ABD\) có:
(định lí tổng ba góc trong một tam giác).
=> \(90^0+\widehat{ABD}+60^0=180^0\)
=> \(150^0+\widehat{ABD}=180^0\)
=> \(\widehat{ABD}=180^0-150^0\)
=> \(\widehat{ABD}=30^0\)
Vậy \(\widehat{ABD}=30^0.\)
Chúc bạn học tốt!
Cho tam giac ABC co AB=AC, M la trung diem cua BC, tren canh AB lay diem D. Chung minh : a) AM vuong goc voi BC, b) Tren ta doi cua tia MD=ME. Chung minh CB la tia phan giac cua goc ACE
cho tam giac ABC vuong tai A , diem D thuoc canh huyen BC . Ke DH vuong goc voi AC (H thuoc AC ) ,tren tia doi cua tia HD lay diem K sao cho HK=HD. Ke DM vuong goc voi AB (M thuoc AB) ,tren tia doi cua tia MD lay diem N sao cho MN=MD. Chung minh A la trung diem cua NK
cho tam giac ABC. Goi M la trung diem BC va AM la tia phan giac cua goc A. Ve MI vuong goc AB, MH vuong goc AC. Chung minh rang:
a, MI = MH
b, Tam giac ABC can
c, Cho AB = 17 cm, AM = 15 cm. Tinh BC
d, Tren tia doi cua tia BC lay diem D, tren tia doi cua tia CB lay diem E sao cho BD = CE. Chung minh: tam giac AED can
