已知α∈

,tanα=

,求:
(1)tan2α的值;
(2)sin

的值.
(1)
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(2)

(1)因為tanα=

,所以tan2α=

.
(2)因為α∈

,所以2α∈(0,π).
又tan2α>0,所以sin2α=

,cos2α=

.
所以sin

=sin2αcos

+cos2αsin
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.
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