sin(π/4+θ)*sin(π/4-θ)=2/5,则cos2θ=

化简求值sin^4θ+sin^4(π/3-θ)+sin^4(π/3+θ) sin^4θ+sin^4(π/3-θ)+sin^4(π/3+θ)化简求值 已知sin(π+θ) sin(x+π/4) sin(阿尔法-π/4) sin(-π/4)求值 sin(π/4+θ)*sin(π/4-θ)=2/5,则cos2θ= 2(sinθ+cosθ)= 2√2sin（θ+π/4)为什么?; （-π/2 提问sin(π/4-θ)=1/3,则sin(π/4+θ)= 化简：2sin(π/4+θ)sin(π/4-θ)=? 证明sinθ+cosθ=根号2sin(θ+π/4) （cosθ＋sinθ）＝√2sin（θ＋π／4） 已知sinθ=4/5,sinθcosθ sin(θ-5π)cos[(-π/2)-θ]cos(8π-θ)}/sin[θ-(3π/2)]sin(-θ-4π)我晕，正的还是负的 若sin(θ/2)=4/5,且sinθ 求值：（tan10°-√3）×cos10°/sin50° 求证：[sin（2α+β）]/sinα- 2cos（α+β）=sinβ/cosα 化简cosθ+cos（θ+2π/3）+cos（θ+4π/3） 证明：sin（α+β）sin（α-β）=sin^2α-sin^2β 2sin(x+π/4)sin(x-π/4)=? sin(x+π/4)sin(x-π/4)等于什么?