cos^4π/8sin^4π/8等于cos^4π/8乘以sin^4π/8等于

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 sin kπ/4（k从1到n）的和为什么等于{cos[π/8]-cos[(n+1/2)π/4]}/2sin(π/8)? sinαcosα=1/8且π/4〈α〈π/2,则cos^4α-sin^4α的值等于? sinαcosα=1/8且π/4〈α〈π/2,则cosα-sinα的值等于? sinπ/8×cosπ/8等于多少? sin（π/4-x)为什么等于cos(x+π/4) 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? 化简sin(α-5π)/cos(3π-α)×cos(π/2-α)/sin(α-3π)×cos(8π-α)/sin(-α-4π) cos(α+π/4)为什么等于根号2/2cosα-根号2/2sinα? 为什么cos(β-α)=cos(α-β),已知sin(α- β)cosα-cos （ β- α )sin α =3/5,β是第三象限角,则sin ( β+5π/4）=因为cosα是偶函数,所以cos（β-α）=cos（α-β）,则原式=sin（α-β）cosα-cos（β-α）sinα=sin（α-β）co sin等于4/5 cos等于多少 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 若(cosα-sinα)/(cosα+sinα)=4,则tan(π/4-α)等于 若(cosα-sinα)/(cosα+sinα)=4,则tan(π/4-α)等于 sin^4(3π/8)-cos^4(3π/8)的结果等于答案是√2/2 sin^4π/8 +cos^4π/8 (cos(π/8))^4-(sin(π/8))^4