cos x=1-x^2/2!+x^4/4!-x^6/6!…… 这个等式是怎么得到的~

求解三角函数 cos 2 X (1 - 2 sin ^2 2 X) + cos 4 X ( 1 + cos 2 X)cos 2 X (1 - 2 sin ^2 2 X) + cos 4 X ( 1 + cos 2 X) = cos 2 X cos4X (1 + cos 2 X) = cos 4 X (1 +2cos 2X) = 0 求证（cos^2 x-sin^2 x)(cos^4 x+sin^4 x)+1/4 sin 2x sin 4x=cos 2x cos 2x(1-2sin^2 2x) + cos 4x (1+cos 2x)= 证明cos 2x cos x=1/2(cos x+cos 3x) 求证(3-sin^4 x-cos^4 x)/2cos^2 x=1+tan^2 x+sin^2 x 化简f(x)=cos(-x/2)+cos(4k+1/2-x/2) 若sinx+sin^2x=1,则cos^2x+cos^4x=? 证明sin^4x-cos^4x=sin^2x-cos^2x 求证sin^4x-cos^4x=sin^2x-cos^2x 证明sin^2(x)+cos^2(x+30)+sin(x)cos(x+30)=3/4 求证（cos^2x-sin^2x)(cos^4x+sin^4x）+1/4sin2xsin4x=cos2x 一道三角函数证明题sin^4 X+cos^4 X=1-2sin^2 X cos^2 X 证明1-sin^6x-cos^2x/1-sin^4x-cos^4x=3/2 求证：1-cos^4x-sin^4x/1-cos^6x-sin^6x=2/3 已知函数f(x)=6cos^4x-5cos^2x+1/2cos^2x-1,求f(x)的定义域值域 急,matlab解非线性方程组用什么函数呢 方程如下所示：(cos(x(1))*cos(x(3))-sin(x(1))*cos(x(2))*sin(x(3)))*(194-x(4))*x(7)+(cos(x(1))*sin(x(3))+sin(x(1))*cos(x(2))*cos(x(3)))*(145-x(5))*x(7)+sin(x(1))*sin(x(2))*x(6)*x(7)-1=0;(-sin(x(1 求函数y=7-4sin(x)cos(x)+4cos^2(x)-4cos^4(x)值 化简sin^4x+cos^2x