证明Y=1/2sin(π/6-2x)+5/4的单调递减区间

证明Y=1/2sin(π/6-2x)+5/4的单调递减区间 一道三角恒等式证明题请证明sin(x+y)sin(x-y)=sin^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tan^2x=2*tan^2y+1,求证sin^2y=2sin^2x-1 如果 2sin(x-y)=sin(x+y),证明 tanx= 3 tany 证明sin(x+y)sin(x-y)=（sinx）^2-(siny）^2. 证明sinx+siny+sinz-sin(x+y+z)=4sin((x+y)/2)sin((x+y)/2)sin((x+y)/2) 证明tan(x+y)+tan(x-y)=sin2x/cos^2x-sin^2y 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) 1-(sin^6x+cos^6x)=3sin^2xcos^2x 如何证明? y=[√（1+sin^2x)+sinx+1]/[√（1+sin^2x)+sinx-1]判断并证明奇偶性 证明cosx-cos(x+2y)/2siny= sin(x+y)证明cosX-cos(x+2y)/2siny= sin(x+y) y=12sin(2x+π/6)+5sin(π/3-2x)最大值 y=12sin(2x+π/6)+5sin(π/3-2x)的最大值 请问怎么证明sinX+sin(X+Y)+sin(X+2Y)/cosX+cos(X+Y)+cos(X+2Y)=tan(X+Y), sin(x+y)-sinx=2cos(x+1/2y）sin(1/2y)的详细证明步骤.越详细越好. 判断函数y=lg[sinx++√(1+sin^2x)]的奇偶性并证明