sin^4π/8-cos^4π/8=?

cos^6(π/8)-sin^6(π/8)=求值,[cos^2(π/8)-sin^2(π/8)][cos^4(π/8)+sin^4(π/8)+cos^2(π/8)sin^2(π/8)]=cos(π/4)[1-cos^2(π/8)sin^2(π/8)]=cos(π/4)[1-[sin^2(π/4)]/4]==7√2/16 sin^4π/8-cos^4π/8=? sinθcosθ=1/8,θ∈(π/4,π/2),求cosθ-sinθ的值 为什么-[cos²(π/8)-sin²(π/8)]=-cos(π/4) 若 sinθ ·cosθ=1/8,求 sinθ +cosθ?怎样用单位圆确定 sinθ 和cosθ大若 sinθ ·cosθ=1/8,求 sinθ +cosθ?怎样用单位圆确定 sinθ 和cosθ谁大谁小?θ属于（π/4，π/2），关键是怎样用单位圆比较大小 sinπ/8cosπ/8=( ) 化简sin(α-5π)/cos(3π-α)×cos(π/2-α)/sin(α-3π)×cos(8π-α)/sin(-α-4π) sin^4π/8 +cos^4π/8 (cos(π/8))^4-(sin(π/8))^4 cos^4(π/8)-sin^4(π/8)等于? cos^4π/8sin^4π/8等于cos^4π/8乘以sin^4π/8等于 已知sinα+cosα=1/5,求值：（1）sinαcosα；（2）sin³α+cos³α；（3）sin四次方α+cos四次方αsinα+cosα=-1/5,且α∈（0,π）,则tanα=_________sinα+cosα=-1/8,且α∈（π,5/4π）,则sinα-cosα=___________已知sec cos 5π/8 cos π/8 + sin 5π/8 sin π/8= 化简：[1+2sin(α+2π)*cos(α-2π)]/[sin(α+4π)+cos(α+8π)] sin(4分之π-β)cosβ+cos(4分之π-β)sinβ= cos^2(π/4+α)=(cos(π/4)cosα-sin(π/4)sinα)² cos^2(π/4+α)是怎么等于(cos(π/4)cosα-sin(π/4)sinα)²的? 由cos(a+b)=cos a cos b-sin a sin b cos(a-b)=cos a cos b+sin a sin b解题设a为锐角,证：1、2分之根3乘cos a + 2分之1乘sin a=cos(6分之π-a)2、cos a-sin a=根号2cos(4分之π+a) 已知θ∈（π/4,π/2）,且sinθ×cosθ=1/8,则cos²θ×cos²θ－sin²θ×sin²θ=（ ）