△ABC中，角A，B，C所对的边分别为a，b，c，若a=2，b=2，sinB+c_爱下问搜题

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问题填空题

△ABC中，角A，B，C所对的边分别为a，b，c，若a=

2

，b=2，sinB+cosB=

2

，则角A的大小为______．

答案

由sinB+cosB=

2

得1+2sinBcosB=2，即sin2B=1，

因为0＜B＜π，所以B=45°，b=2，所以在△ABC中，

由正弦定理得：

2

sinA

=

2

sin45°

，

解得sinA=

1

2

，又a＜b，所以A＜B=45°，所以A=30°．

故答案为

π

6

完形填空

When I was in primary school, I had a big argument a boy in my class. l can't remember what it was about, but I have never forgotten the lesson I learned that day. I was that I was right and he was wrong. However, he believed that I was wrong and he was right. The teacher decided to teach us a lesson. She came up with a good idea. She brought of us to the front of the class ,then she placed the boy on one side of her grey desk and me on .In the middle of the desk was a large, round object (物体). It was clear for me that it was black. She asked the boy what color the object was. "White," he answered in a loud voice. I couldn't believe that the object was white. One more argument started between the boy me, this time about the color of the object. The teacher told me to go where the boy was standing and told him to come where I had been. We changed and then she asked me what the color of the object was. I had to answer, "White. " It was then that I what was wrong. It was an object with two differently colored sides, and from his side it was white only, from my side it was black. My teacher taught me a very important 1esson that day: You must stand in other persons' position (位置) and look at the situation through their eyes truly understand their ideas.

C．in order to

D．in order that

单项选择题

在渤海面上背真风而立，低压在（）

A.右后

B.左后

C.右前

D.左前