若cos (x+30°)+sin x =4/5,则cos (2x-60°)等于?

sin（sin（sin（sin（x）=cos（cos（cos（cos（x）,X等于多少? cos x /sin x= 若cos (x+30°)+sin x =4/5,则cos (2x-60°)等于? 证明sin^2(x)+cos^2(x+30)+sin(x)cos(x+30)=3/4 若cos x-sin x = 0.5,则cos^3 x-sin^3 x = 若f(cos x)=cos 3x ,那么f(sin 30°）的值为 若f（sin x+cos x）=sin x·cos x,则f（cos 派/6）=? 已知tan=2,求(cos x+sin x)/(cos x-sin x)+sin^2x y=2cos x (sin x+cos x) 已知sin(x)+3cos(x)=2,求sin(x)-cos(x)/sin(x)+cos(x)=? 设x为锐角,若cos(x+30°)=4/5 ,sin(2x+15°)等于? 若x小于60,且sin(60-X)=12/15,则cos(30+X)=? 若x小于60,且sin(60-X)=12/15,则cos(30+X)=? 若SIN X*COS X =1/3,已知0 sin²x+cos²x= y=(sin x + COS x)^2 cos2x=cos^x-sin^x 为什么? sin(x/2)cos(x/2)=