设sin2α=-sinα,α属于(2分之π,π),则tan2α的值为?
1个回答
由题
sin2α=2sinαcosα=-sinα
又,α属于(2分之π,π),sinα≠0
所以,cosα=-1/2
α=2π/3
tan2α
=tan4π/3
=tanπ/3
=√3
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