Question

θ第二象限角 根号下sin^2θ-sin^4θ可化简为 如题

Answer 1

√(sin^2θ-sin^4θ)
=√((sinθ)^2(1-(sinθ)^2))
=√(sinθcosθ)^2
=|sinθcosθ|
因为θ在第二象限,所以sinθ>0,cosθ