求证|sinx-siny|=|2sin[(x-y)/2]cos[(x+y)/2]|

求证sin（2x+y)/sinx-2cos(x+y)=siny/sinx 求证：sin(2x+y)/sinx-2cos(x+y)=siny/sinx 求证sinx+siny=2sin(x+y)/2*cos(x-y)/2 求证:sinx+siny=2sin(x+y)/2cos(x-y)/2 求证|sinx-siny|=|2sin[(x-y)/2]cos[(x+y)/2]| 已知cosa=cosx*siny,cosb=sinx*siny求证：sin^2a+sin^2b+sin^2y=2 求证：sin(2x+y)/sinx-2cos(x+y)=siny/sinx(2)已知5siny=sin(2x+y),求证:tan(x+y)=3/2 tanx 求证.(tanx+tany)/(tanx-tany)=(sinx+siny)/(si求证.(tanx+tany)/(tanx-tany)=(sinx+siny)/(sinx-siny) 求证：sin（x-y）/（sinx-siny）=cos[（x-y）/2]/cos[(x+y)/2]（cosy-cosx）/（sinx-siny）=tan[（x+y）/2] 证明 [sin(2x+y)/sinx]-2cos(x+y)=siny/sinx 证明cosx(cosx-cosy)+sinx(sinx-siny)=2sin(x-y)/2 证明sin(x+y)sin(x-y)=（sinx）^2-(siny）^2. 证明sin(x+y)sin(x-y)=sinx-siny 三角函数题目：已知：cosa=cosx*siny cosb=sinx*siny 求证：sin^2*a+sin^2*b+sin^2*ysin^2*a+sin^2*b+sin^2*y 应该是 sin^2a+sin^2b+sin^2y =2 arcsin(sinx+siny)+arc(sinx-siny)=kπ/2,K为奇数,求sin^2x+sin^2y的值 一道简单的三角比证明题求证：4sin[(b-c)/2]sin[(a-b)/2]sin[(c-a)/2]=sin(b-c)+sin(a-b)+sin(c-a)sin2x(cos2y-1)+sin2y(cos2x-1) =-2sin2x(siny)^2-2sin2y(sinx)^2有一个负号啊~但是另一边化简出来没有负号，难道cos2y=2(siny)^2+ cosx-cosy=1/2,sinx-siny=1/3,sin(x+y)=RT sinx-siny=1/3,cosx-cosy=2/3,sin(x+y)=?