sin(x+π/6)=1/2,则cos(π/3-x)求值

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 已知(1+sin x)/cos x=-1/2,则cos/(sin x-1)=? 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)] sin(x+π/6)=1/2,则cos(π/3-x)求值 已知(1-cos x+sin x)/(1+cos x+sin x)=-2,若x不等于kπ+(π/2),则tan x= 设角a=-35π/6,则2sin(π+α)cos(π-α)-cos(π+α)/ 1+sin^2α+sin(π-α)-cos^2(π+α)sina=sin(-35π/6)=sin(-6π+π/6)=1/2 cosα=根号3/22sin(π＋α)cos(π-α)-cos(π+α)/ [1+sin^2α+sin(π-α)-cos^2(π+α)]=2（-sinα)(-cosα）+cosα/[1+sin² sin(x+1/2π)=cosx?还是cos-x 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 已知cos x/（sin x-1）=1/2,则（1+sin x）/cos x等于? 求证:(sin 2x /(1-cos 2x) )·(sin x /(1+sin x))=tan (π/4-x/2). 1/2[cos(2x)cos(π/6)+sin(2x)sin(π/6)]-1/2[cos(2x)cos(π/6)-sin(2x)sin(π/6)]=1/2sin(2x)请问怎么化得1/2sin(2x)? 若sinx+sin^2x=1,则cos^2x+cos^4x=? 已知sin(x+π/3)=1/4,求sin(2π/3-x)+cos²(π/6-x) 求值sin²x+cos²(π/6+x)+1/2sin(2x+π/6) 怎么证明2(1-sin x)(1+cos x)=(1-sin x+cos x)^2 1-(sin^6x+cos^6x)=3sin^2xcos^2x 如何证明? 若sin x/2 - cos x/2 = 1/3,则sin x=?