cos^4(x)-sin^4(x)等于?是cos^2(x)还是cos2x

sin（π/4-x)为什么等于cos(x+π/4) cos^4(x)-sin^4(x)等于?是cos^2(x)还是cos2x cos^4(x)-sin^4(x)+2sin^x的值等于 Sin(x/2)+cos(x/2)为什么等于根号2倍sin(x/2+派/4)? sin（sin（sin（sin（x）=cos（cos（cos（cos（x）,X等于多少? Sin(x+派/4)换成Cos等于什么啊RT 函数y=cos^4x-sin^4x的最小正周期y=(cos^2x+sin^2x)(cos^2x-sin^2x)为什么等于cos^2x-sin^2x=cos2x谢谢 化简sin^4x-sin^2x+cos^2x 化简:sin^4 x-sin^2 x+cos^2 x 化简cos^4x+sin^4x 化简:cos^4(X)-sin^4(X) 化简sin^4x+cos^2x 化简(sin^2x-cos^4x+cos^2x-sin^4x)/(sin^2x-cos^6x+cos^2x-sin^6x) sin（-x） cos(-x)等于多少 已知sin (x-3pai /4)cos (x-pai /4)=-1/4,则cos 4x 的值等于 若cos (x+30°)+sin x =4/5,则cos (2x-60°)等于? 化简 1-sin^4x-cos^4x/1-sin^6x-cos^6x 化简(1-cos^4x-sin^4x)/(1-cos^6x-sin^6x)