已知tan(π4-α)=-12，α∈(π，32π)，求cosα-sin2α的值．_爱下问搜题

搜题请搜索小程序“爱下问搜题”

问题解答题

已知tan(

π

4

-α)=-

1

2

，α∈(π，

3

2

π)，求cosα-sin2α的值．

答案

由 tan(

π

4

-α)=-

1

2

，得

tan

π

4

-tanα

1+tan

π

4

tanα

=-

1

2

，

∴tanα=3

因α∈(π，

3

2

π)

∴cosα=-

1

10

，sinα=-

3

10

∴cosα-sin2α=cosα-2sinααcosα=-

6+

10

10

．

完形填空

One day in the     __ class everyone is busy drawing pictures, but Xiao Ming is doing _   __.When the bell rings for break (课间休息), Xiao Ming gives his _   _ to the teacher.
The teacher looks at it and gets __   _. “Why did you give me a piece of paper with nothing on it, Xiao Ming?” __   ___ the teacher.
“I’m sorry, sir,” says Xiao Ming. “I _    _ a dog and some __    _ on the paper.”
“Where’s the dog and where’s the bread?” asks the teacher.
“I draw the bread       。When I finish drawing the dog, he _   __ the bread. When I give it to you, he _  _ away,” Xiao Ming answers.

C．angry(生气)

判断题

clear命令负责清除终端屏幕，当使用这个命令于特殊场合时，需要配合该命令的其它命令选项。（）