sin(30.+x)=1/3,cos(120.-2x)的值是?

Sin x-sin y=2/3 cos x-cos y=1/2 求cos(x-y) 1/cos(x) - tan(x) = 3 求sin(x)1/cos(x) - tan(x) = 3求sin(x) (1+cos x-sin x)/(1-sin x-cos x)+(1-cos x-sin x)/(1-sin x+cos x)=? 求证(3-sin^4 x-cos^4 x)/2cos^2 x=1+tan^2 x+sin^2 x cos x/sin x+sin x/(1+cos x) 化简. 解方程：cos^3x-sin^3x=1 求方程 sin^3x+cos^5x=1 若SIN X*COS X =1/3,已知0 求证：1-cos^4x-sin^4x/1-cos^6x-sin^6x=2/3 证明1-sin^6x-cos^2x/1-sin^4x-cos^4x=3/2 化简[1-(sin^4x-sin^2cos^2x+cos^4x)/(sin^2)]+3sin^2x 已知sin[a-b]cos a-cos[b-a]sin a=3/5,b是第三象限角,求sin[b+5π/4]的值第一题1/2cos x-√3/2sin x第二题√3sin x+cos x第三题√2[sin x-cos x]第四题√2cos x-√6sin x 为什么cos(sin(tan x)))=1 怎么证明2(1-sin x)(1+cos x)=(1-sin x+cos x)^2 y=(sin(x)-1)/(cos(x)+(cos(x))/(sin(x)+1)的奇偶性 化简 1/2cos x-根号3/2sin x 根3sin x+cos x 证明成立：[cos(3x)-sin(3x)]/(cosx+sinx)=1-2sin(2x). 若sin x/2 - cos x/2 = 1/3,则sin x=?