证明|sin x|+|cos x|大于等于1

证明|sin x|+|cos x|大于等于1 证明sin^2(x)+cos^2(x+30)+sin(x)cos(x+30)=3/4 怎么证明2(1-sin x)(1+cos x)=(1-sin x+cos x)^2 证明sin^4x-cos^4x=sin^2x-cos^2x 当X大于0时,证明sin(x)小于X. 证明COS（X+Y）COS（X-Y）=COS^2X-SIN^2Y 证明cos(x+y)cos(x-y)= cos^2(x)-sin^2(y) 证明一个sin&cos的等式证明 1+sin^2(x)+sin^4(x)+sin^6(x)=[1-sin^8(x)]/[cos^2(x)] 证明sin x+cos x的最大值等于 根号2 如何证明sin方x+cos方x=1 如何证明sin(x)的积分=-cos(x) 证明 2sin(π+x)cos(π-x)=sin2x 证明：sin^2x+cos^2x=1 证明sin(cos(x))总是小于cos(sin(x))万分先感激! 证明：(1 + tan x) / (sin x + cos x) = 1 / cos x (sinX+sinθ) .(Sinx-sinθ)=sin(x+θ).cos(x-θ)证明 设f(x)=cos x.证明(cos x)'=-sin (cos X-1)^2+sin^2X=2-2cos X 证明题(要过程)