搜题请搜索小程序“爱下问搜题”
问题 选择题
△ABC中，若A=60°，a=
3
，则
a+b-c
sinA+sinB-sinC
等于（　　）
A．2B．
1
2
C．
3
D．
3
2
答案

由正弦定理可得  2r=

a
sinA
=
3
sin60°
=2，（r为外接圆半径）；

a+b-c
sinA+sinB-sinC
=
2rsinA +2rsinB - 2rsinC
sinA+sinB-sinC
=2r=2，

故选A．

填空题

用所给词的适当形式填空。

1. Everyone wants _______ ( achieve) his or her dream.

2. I think Zhang Renjie is much________( realistic)  than us.

3. Wang Baoqiang tried his best to perform and he__________( success) in the

end.

4. What are the rules that a teenager should __________( obey) ?

5. Most people come to realize the________(important) of protecting the earth.
查看答案
选择题

下列各种现象中，能说明液体的表面积越大，蒸发就越快的是（　　）

A．把木材放在烘房里要比放在露天里干得快

B．晴天把洗好的衣服凉出来要比在阴天的时间干得快

C．同样多的酒精和水，在相同条件下酒精干得快

D．洗脸后将毛巾挂在毛巾架上要比把毛巾团放在脸盆内要干得快
查看答案