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+ ΔAHB và ΔCKD có
HB = KD (=1)
góc AHB = góc CKD(=90º)
AH = CK (=3).
⇒ ΔAHB = ΔCKD(c.g.c)
⇒AB = CD (hai cạnh tương ứng)
+ ΔCEB và ΔAFD có
BE = DF (=2)
góc BEC = góc DFA (=90º)
CE = AF (=4).
⇒ ΔCEB = ΔAFD ( c.g.c)
⇒ BC = AD (hai cạnh tương ứng)
b) ΔABD và ΔCDB có
AB = CD
AD = BC
BD cạnh chung
⇒ ΔABD = ΔCDB (c.c.c)
⇒ góc ABD = góc CDB (hai góc tương ứng)
Vậy AB // CD ( hai gó so le trong bằng nhau )
k minh nha
(hình hơi xấu, thông cảm nha)
a) Xét \(\Delta AEB\)và \(\Delta DFC\) có:
AE = DF
\(\widehat{AEB}=\widehat{DFC}=90^o\)
BE = CF
Do đó: \(\Delta AEB=\Delta DFC\) (c.g.c)
Suy ra: AB = DC (đpcm)
Xét \(\Delta BMC\) và \(\Delta DNA\) có:
MC = NA
\(\widehat{BMC}=\widehat{DNA}=90^o\)
BM = DN
Do đó: \(\Delta BMC=\Delta DNA\)
Suy ra: BC = AD (đpcm)
b) Xét \(\Delta ABD\) và \(\Delta CDB\) có:
AB = CD (câu a)
BC = AD (câu a)
BD là cạnh chung
Do đó: \(\Delta ABD=\Delta CDB\) (c.c.c)
Suy ra: \(\widehat{ABD}=\widehat{CDB}\) (so le trong)
=> AB // CD (đpcm)
1. did- learn
2. am having
3. Is
4. have ever eaten
5. is
6. did-save
7. bought
8. didn't drink
9. does- need
10. have never enjoyed
Chúc bạn học tốt :v
Model traffic light are an American invention . Red-green system were installed in Cleveland in 1914 . Three color signals were traffic light in New York in 1918 . They used to be operated by hand from a tower in the middle of street.The first light of the type appeared in London,on the junction between St.James and Piccadilly,in 1925. Automas signals were installed a year later .In the past , traffic lights used to be very special . In New York , some light used to put a statue on top .
1.They putted a new poof last year
2.Oil lamp was used (?) year ago
3.The fowls are felt twice a day
4.Are the windows often cleaned by him
5.sai de.Any trees aren't grown in her garden
6.His car is washed every Sunday morning
lieu an nhieu nha
HOCTOT
1. a, people b, teach c, please d, pleasure
2. a, things b, maps c, events d, reports
1.is reading
2.travel
3.student ko có ''s''=>do,nếu bạn viết thiếu thì là does
4.find
5.is watching
6.are reading
7.won't come
8.is playing
9.goes
10.are you going
11.studies
12.fix
13.are doing
14.will be
15.drawing
hk tốt
1.is reading 7.won't come 13.is doing
2.travel 8.is playing 14.will be
3.go 9.goes 15.drawing
4.find 10.is......going
5.watches 11.studies
6.read 12.fixes
GOOD LUCK !
1.Her clothes are washed everyday by Hoa.
2. Me was seen at the superman by Tuan.
3.English has been studied for 5 years.
4.Uniforms should be wear uniform.
5.English is spoken all over the world.
Nếu đúng nhớ k cho mình nhé.
Photography là một môn học sao?