已知tanα＝2,求sin2α的值

已知tanα＝2,求sin2α的值
已知tanα＝2,求sin2α的值

已知tanα＝2,求sin2α的值
sin2α
=2sinacosa
=2sinacosa/(sin^2 a+cos^2 a)
=2tana/(tan^2 a+1)
=2*2/(2^2+1)
=4/5

sin2α=2tana/(1+tan^2a)=4/5

sin2α
=2sinacosa
=2sinacosa/(sin^2 a+cos^2 a)
=2tana/(tan^2 a+1)
=2*2/(2^2+1)
=4/5

sin2a=2*sina*cosa tana=sina/cosa