cos(2x+60`)cos(x-30`)+sin(2x+60`)sin(x-30`)=1/2求这题的题解...60` 是60度.

化简cos 2x (cos(x))^-2导数 cos(x^2)dx cos x>-1/2 证明cos 2x cos x=1/2(cos x+cos 3x) cos x cos x sin(45-3x)*cos(60-3x)-cos(30+3x)*sin(45+3x) ? sin(45-3x)*cos(60-3x)-cos(30+3x)*sin(45+3x) 证明sin^2(x)+cos^2(x+30)+sin(x)cos(x+30)=3/4 2cos x (sin x -cos x)+1 y=2cos x (sin x+cos x) 化简sin(x)cos(x)cos(2x) 化简sin(x)cos(x)cos(2x) sin x cos x cos 2x 化简 若cos (x+30°)+sin x =4/5,则cos (2x-60°)等于? 2（cos x）^2=1+cos 2x, cos(∏x)^2求导?是cos（pie x)^2