Предмет: Геометрия, автор: маша21112001

отрезки АС и ВД пересекаются в точке О, причем АО =15см, ВО=6см, СО=5см,ДО=18см. Докажите что четырехугольник АВСД- трапеция

Ответы

Автор ответа: 21fizika

рассм. тр-ки ВСО и АОД; они подобны, т.к. СО/АО=ВО/ОД; 5/15=6/18;
1/3=1/3; углы ВОС и АОД равны (вертикальные); отсюда угол СВД=
=углу ВДА; это накрест лежащие углы при параллельных ВС и АД и секущей ВД, основания ВС и АД параллельны, значит АВСД - трапеция.

Предыдущий вопрос

Следующий вопрос

Похожие вопросы

Предмет: Физика, автор: lusenkooleg967

ВСЕ НА ФОТЦІ СРОЧНО СРОЧНО
ТІЛЬКИ ПЖ ЗРОБІТЬ

7 лет назад

Предмет: Химия, автор: kalimab2008

Высшую валентность азот проявляет в оксиде: а) N2О; в) NО; с) N2О3; д) NО2; е) N2О5;

7 лет назад

Предмет: Английский язык, автор: rmeshetov09

1. I’m ___ English student. A) a B) an C) the D) --- E) is
2. You are ___ good friend! A) a B) an C) the D) --- E) is
3. My aunt is ___ art teacher. A) a B) an C) the D) --- E) is
4. How old are you?
A) Tom Hardy B) I am from Canada C) I am fourteen D) I can use computers E) Yes, I do.
5. What’s your name?
A) Tom Hardy B) I am from Canada C) I am fourteen D) I can use computers E) Yes, I do.
6. Andrea isn’t British. He ___ American. A) am B) is C) are D) isn’t E) has
7. Mark and John ____ Australian. They ____ British.
A) aren’t, are B) aren’t, am C) are, arent D) are, is E)aren’t, have
8. Nice to meet you.
A) London, and you? B) Nice to meet you too. C) I am from Birmingham! D) Simon.
E) I am fine.
9. Do you read stories in English at home?
A) Yes. B) No. C) Yes, I do. D) I read stories in English at home. E) Yes, I read.
10. Can you play the piano?
A) Yes, I can. B) Yes, I play the piano. С) No, I don’t. D) Yes, I do. E) Yes, I like it.
11. How old are you? And how old are _____ parents? A) your B) my C) our D) yours E) his
12. She is a new student. ____ brother is in a different class.
A) his B) her C) your D) my E) their
13. He is my cousin. ____ father is my favourite uncle!
A) his B) her C) your D) my E) their
14. They are brothers. _____ sister is at university.
A) his B) her C) your D) my E) their
15. How old is your sister? She is 14.
A) fourteenth B) forteen C) fourty D) fourteen E) forty
16. My birthday is in spring, on the 5th of ____.
A) October B) December C) January D) June E) March
17. My grandmother is very old. She is 86 years old.
A) eighty-six B) eighteen-six C) eighty- sixth D) eighty E) sixty
18. Five – fifteen – fifty; seven – seventeen – seventy; nine - _____ - ______.
A) Ninety-nineteen B) nineteen-ninety C) nineteen-nineteen D) ninety-ninety E) nineteen ninty
19. There are twelve ______ and one blackboard in the classroom.
A)desk B) windows C) plant D) cupboards E) chairs
20. There are five _____ and six _____ in the photo.
A) man, woman B) mans, womans C) men, women D)woman, men E) men, woman
21. He is your teacher. Listen to ____. A) he B) him C) she D) her E) it
22. I am here. Sit next to ____. A)my B) it C) us D) me E) them
23. I have a big, comfortable ____ in my bedroom.
A) carpet B) computer C) bed D) curtains E) lamp
24. My aunt has a ____, _____ hair.
A) big, blonde B) small, dark С) blonde, dark D) long, short E) short, dark
25. He is a ______ boy from Argentina. A) small B) big C) young D) thin E) old

7 лет назад

Предмет: Физика, автор: Аноним

(Применение) учет влажности в разных областях народного хозяйства

10 лет назад

Предмет: Экономика, автор: tanyalevina98

Почему люди от простого собирательства натуральных продуктов перешли к исскуственному производству благ?

10 лет назад