已知在直角梯形ABCD中,上底CD=4,下底AB=10,非直角腰BC=4
|
如图,过C作CE⊥AB于E,则四边形AECD是矩形
,
∴AE=CD=4,
在Rt△BEC中,BE=6,BC=4
,3
∴cos∠B=
=BE BC
=6 4 3
,3 2
∴∠B=30°.
故答案为30°.
已知在直角梯形ABCD中,上底CD=4,下底AB=10,非直角腰BC=4
|
如图,过C作CE⊥AB于E,则四边形AECD是矩形
,
∴AE=CD=4,
在Rt△BEC中,BE=6,BC=4
,3
∴cos∠B=
=BE BC
=6 4 3
,3 2
∴∠B=30°.
故答案为30°.
阅读理解。 | ||
Su Hua is studying at Cambridge, UK. She has bought a bicycle and is worried about security (安全). Her friend, Kate, found this article and sent it to her.
| ||
1. Which part of the text gives you information on how to lock up your bicycle when you leave it? | ||
A. Locks. | ||
2. The underlined phrase “act as a deterrent to a thief” means ______. | ||
A. help you recognize your bike B. help the police find your bicycle C. stop someone stealing your bicycle D. stop you worrying about your bike | ||
3. The article advises you to keep a record of your bicycle _______. | ||
A. in the bike shop and your computer B. in the police station and a security company C. in a security company and your university D. by yourself and in a security company | ||
4. The main purpose of this article is ______. | ||
A. to tell you what to do if your bicycle is stolen B. to suggest ways of keeping your bicycle safe C. to give you advice on where to buy a good lock D. to say why you shouldn’t keep your bicycle in a quiet place |