cos^22x+sin^22x=1吗?

sin（sin（sin（sin（x）=cos（cos（cos（cos（x）,X等于多少? 求证（cos^2 x-sin^2 x)(cos^4 x+sin^4 x)+1/4 sin 2x sin 4x=cos 2 sin(1/x)-cos(1/x)/x 证明(1-2sin x cos x )/(cos^2x-sin^2x)=(1-tan x)/(1+tan x) 已知函数f(x)=cos^4x-2cos^22x+sin^2x的最小正周期 已知tan=2,求(cos x+sin x)/(cos x-sin x)+sin^2x Matlab编程问题 cos(x*y)*cos(x*(1-y))-0.5x*sin(x*y)*sin(x*(1-y))= 证明：(1 + tan x) / (sin x + cos x) = 1 / cos x 已知f(x)=sin(x/2) + cos(x/2) +[cos(x/2)]^2-1/2 化简f(x)=2cos(x/2)·(sin(x/2)+cos(x/2))-1 已知函数f(x)=2Cos x(Sin x-Cos x)+1 Sin x-sin y=2/3 cos x-cos y=1/2 求cos(x-y)