已知α∈（0,π/2）2sin²α=cos2α-sin2α 求tanα的值 若β∈（π/2,π）且sinβ=-2√5/5,求α+β
已知α∈（0,π/2）2sin²α=cos2α-sin2α 求tanα的值
若β∈（π/2,π）且sinβ=-2√5/5,求α+β
人气：123 ℃ 时间：2020-02-02 13:00:53
解答
1、2sin²α=cos2α-sin2α ,2sin²α=2cos²α-1-2sinα cos α2tan²α=2-1/cos²α-2tana=2-(1+tan²a)-2tana3tan²α+2tana-1=0,tana=-1,tana=1/3,已知α∈（0,π/2）,∴tana=1/32...
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