cos(x+0.25π)=5/13 x怎么算

cos(x+0.25π)=5/13 x怎么算 cos(0.25π-x)= 已知cos(x+π/12)=-5/13,x是第三象限角,求cos(x-π/6)的值 已知cos(x+π/12)=-5/13,x是第三象限角,求cos(x-π/6)的值 解方程 cos x=9/13 x[0,π] 三角函数解方程 (cos 3x)^3+ (cos 5x)^3 = 8 (cos 4x)^3 (cos x)^3 2sin^2x - 5sin x cos x=3 cos^2x,求X, 为什么cos(2x-π/3)-sin(5π/6) =cos(2x-π/3)? cos(2x-π)/[根号2cos(x+π/4)]=-1/5,0 化简sin(x)(cos(x)+cos(3x)+cos(5x)+cos(7x)) 设sin(π/4-x)=5/13,则cos2x/cos(π/4+x)=_______ 设sin(π/4-x)=5/13,则cos2x/cos(π/4-x)=_______ 函数f(x)=2cos(2x+5/2π)+3cos(4π+2x)的值域 是﹣根号13,根号13吗? cos(π/6-x)=根号3/3则cos(5π/6+x)-sin(x-π/6)的平方 cos(97x)=x cos x /sin x= cos(x)看到这个 cos(x)－cos(y)=? 已知0《x《π/4,sin（π/4-x）=5/13,求cos2x/cos（π/4+x）