sin(π/4+θ)*sin(π/4-θ)=2/5,则cos2θ=
2sinθ+cosθ/sinθ-3cosθ=-5,求cos2θ+4sinθ
已知sinθ+cosθ=2sinα,sinθcosθ=(sinβ)^2,求证4(cos2α)^2=(cos2β)^2
若sin(π/4+α)=sinθ+cosθ,2sin^2β=sin2θ,求证:sin2θ+2cos2β=3
若2sin(π/4+a)=sinθ+cosθ,2sin^2β=sin2θ,求证sin2a+(1/2)cos2β=0.
若2sin(π/4+a)=sinθ+cosθ,2sin^2β=sin2θ,求证sin2a+(1/2)cos2β=0
求证cos^4θ-sin^4θ=cos2θ
cos2θ=根号2/3,则sin^4θ+cos^4θ=
若cos2θ=√2/3,则sinθ^4+cos^4的值为
cos2θ=√2/3,则cos^4-sin^4的值为
证明2sin(π/4+α)sin(π/4-α)=cos2α
cos2α/[sin(α-π/4)]=-根号2 /2,cosα+sinα=?
已知sinθ/2+cosθ/2=2根号3/5,则sinθ= ,cos2θ=