tan(x)=2求sin(x)cos(x)=?

已知tan=2,求(cos x+sin x)/(cos x-sin x)+sin^2x 证明(1-2sin x cos x )/(cos^2x-sin^2x)=(1-tan x)/(1+tan x) 证明1-tan^2x/1+tan^2x=cos^2x-sin^2x 已知tan x=-3/4,求sin x ,cos x ,cot x 的值. 已知tan x=-2且x是第二象限的角求sin x和cos x 若tanx=2,求:sin(tt/2+x)*cos(tt/2-x)*tan(-x+3tt)/sin(7tt-x)*tan tan(x+y)tan(x-y)=sin^2x-sin^2y/cos^2x-sin^2y 顺便问一下. tan,sin, f(x)=|sin x+cos x+tan x+cot x+sec x+csc x|最小值 三角函数题.已知tanx=2.求(sin(π-x)cos(2π-x)sin(-x+3π/2))/tan(-x-π)sin 已知(x)=[sin(π-x)cos(2π-x)tan(-x+π)]/[cos(-π/2+x)] 求sin^2(x)+tan^2(x)+csc^2(x)+sec^2(x)+cos^2(x)+cot^2(x)=31里,x 求极限x趋于0时(1-cos(x/2))x / (tan x-sin x)