已知π/2＜απ 则根号sin平方α-sin4次方α

已知π/2＜απ 则根号sin平方α-sin4次方α

π/2＜α<π
√(sin^2α-sin^4 α)
=√[sin^2α(1-sin^2 α)]
=√[sin^2αcos^2 α]
=-sinacosa
=-1/2sin2a