已知A，B，C三点的坐标分别是A（3，0），B（0，3），C（cosα，sinα

发布时间：2017-04-15 07:30 │ 来源：www.tikuol.com

题型：解答题

问题：

已知A，B，C三点的坐标分别是A（3，0），B（0，3），C（cosα，sinα），α∈(

，

3π

)，若

•

=-1，则

1+tanα

2sin2α+sin2α

的值为（　　）

A．-

B．-

C．2

D．3

考点：同角三角函数的基本关系式向量数量积的运算

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home in a hurry.     3
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A. It's a shoe box.
B. Tina is my sister.
C. So she put on the shoes and left.
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