1-1/x=cos(15/x)

1-1/x=cos(15/x) 证明cos 2x cos x=1/2(cos x+cos 3x) 2（cos x）^2=1+cos 2x, y=(cos x-2)/(cos x-1)的值域 Cos x=-1/2 y=cos^2 x-cos x +1的值域y=cos^2 x+cos x +1的值域, (1+cos x-sin x)/(1-sin x-cos x)+(1-cos x-sin x)/(1-sin x+cos x)=? cos x/sin x+sin x/(1+cos x) 化简. cos x>-1/2 / (cos x + 1 ) dx 怎么证明2(1-sin x)(1+cos x)=(1-sin x+cos x)^2 证明：(1 + tan x) / (sin x + cos x) = 1 / cos x y=(sin(x)-1)/(cos(x)+(cos(x))/(sin(x)+1)的奇偶性 cos(x)=1 +sin(x)cos(x)用两种方法求x 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：tan x/2=sin x/(1+cos x) 求证：1-sin(x)=cos(x)*tan(x/2) f'(sin x)=1-cos x 求f''(x)