cos(3π/8)*sin(5π/8)=?

cos 5π/8 cos π/8 + sin 5π/8 sin π/8= cos(3π/8)*sin(5π/8)=? sinπ/8cosπ/8=( ) 化简sin(α-5π)/cos(3π-α)×cos(π/2-α)/sin(α-3π)×cos(8π-α)/sin(-α-4π) 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 (cosπ/8+sinπ/8)（cos^3π/8-sin^3π/8） (cosπ/8+sinπ/8)（cos^3π/8-sin^3π/8）. (cos π/8+ sin π/8 ) (cos^3 π/8+sin^3 π/8 )的值. cos(π/3-α)=1/8,则cosα+（根号3）sinα的值为____已知cosα-cosβ=1/2,sinα-sinβ=1/3,求cos(α+β)的值 已知8sinα+10cosβ＝5,8cosα+10sinβ＝5√3,求证：sin(α+β)=－sin(π/3+α) 化简sin（a-5π）cos（-π/2-a）cos（8π-a）/sin（a-3π/2）sin（-a-4π） 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 化简sin（a-5π）cos（-π/2-a）cos（8π-a）/sin（a-3π/2）sin（-a-4π） 已知sinα+cosα=4/5且3π/22,若sinα+sinβ+sinγ=0,cosα+cosβ+cosγ=0,则cos(α-β)的值 已知cos(π-α)=8/17,求sin(α-5π),tan(3π+α) 求SINπ/64 COSπ/64 COSπ/32 COSπ/16 COSπ/8 已知sin(3π+α)=2cos(α-4π)求cos(π/2 -α)+5sin(π/2 +α)/2cos(π+α)-sin(-α) 【三角函数】已知sin(α-π)=2cos(2π-α),求[sin(π-α）+5cos（2π-α)]/[3cos(π-α）-sin（-α)]