设sin(π/4+θ)=1/2,求sin2θ.

设sin(π/4+θ)=1/2,求sin2θ. 设π＜θ＜2π,cosθ/2=α,求（1）sinθ的值；（2）sin²θ/4的值. 设α,β,γ∈(0,π/2)且(sinα)^2+(sinβ)^2+(sinγ)^2=1求函数y=(sinα)^3/sinβ+(sinβ)^3/sinγ+(sinγ)^3/sinα 的最小值. 设sin(π/4-a/2)cos(π/4-a/2)=1/6,求sin2a 设sin(a+π/2)=-1/4 且sin2a大于0 求sina tana 2sinθ = cosθ + 1,怎么求sin 设sinα-cosα=1/2,求sinα*cosα= 设tan2θ =-2根号2,2θ∈（π/2,π）求(2cos^2θ-2-sinθ-1)/(sinθ+cosθ) 已知sinθ+sin^2θ=1,求3cos^2θ+cos^4θ-2sinθ+1 设sin(α+π/2)=－1/4,且tanα＞0,求sinα,cosα和tanα的值 sin(π/4+α)sin(π/4-α)=1/4 求2sin^2(a) -1+tana-1/tan 已知sin(x+π/6)=1/4,求sin(5π/6-x)+sin^2(π/3-x) 设sinθ+cosθ=√2/3,π/2sinθ^3是sinθ的3次 设向量a=(1,cos2Θ),b=(2,1),c=(4sinΘ,1),d=(1/2 sinΘ,1),其中Θ∈(0,π/4).1.求a*b-c*d的取值范围.a*b-c*d=2+cos2Θ-(2sinΘsinΘ+1)=2+cos2Θ+cos2Θ-2 (cos2Θ=1-2sinΘsinΘ)=2cos2ΘΘ∈(0,π/4)所以a*b-c*d∈(0,2)请问(cos2Θ=1-2sinΘsinΘ) 2sin(π/4+a)=sinθ+cosθ,且2sin^2b=sin2θ,求sin2a+1/2cos2b 为什么sin-sin^2=1/4 已知sin(a/2+π/6)=1/4求sin(π/6+a) sinθcosθ=1/8,θ∈(π/4,π/2),求cosθ-sinθ的值