已知cos(α π/4)=3/5,-3π/2

已知cosα=-3/5,α属于(π/2,2π)则cos(α-π/4)= 已知cos(θ+π/4)=3/5,π/2 已知cosα=1/3,α属于(π,2π),则cosπ/2等于 已知cos(π\3-2)=1\3,则cosα+根号3sinα= 已知cos(π/2+α)=2sin(α-π/2),求[sin^3(π+α)+cos(α+π)]/[5cos(5π/2-α 已知(sinα-cosα)/(sinα+cosα)=1/3,则cos^4(π/3+α)-cos^4(π/6-α)的值为 ①化简[sin(2π+α)*cos(7π-α)]/cos(-α)②已知cosθ=-3/5,θ∈(π/2,π),求sin( 已知α∈（0,π/2),且2sinα-sinαcosα-3cosα=0.求[sin(α+π/4)]/[sin2α+cos 已知sin(5π-α)=√2cos(3π/2+β),)√3cos(-α)=-√2cos(π+β),0 1.已知cosα=12/13,α∈(3π/2,2π),求cos(α+π/4). 已知cos（π/4 - α）＝- 3/5,α∈（π/2,π）,求cosα 已知tan（π-α）=2,求sinα-2sinαcosα-cosα／4cosα-3sinα的值