sina +-√3cosa=2sin(a +-π /3)是怎么推出来的,

已知(sina+cosa)/(sina-cosa)=3 则2sin'a+(sina-cosa)'=? sina=2cosa,求(1)3sina+2cosa(2)sin²a+sina×cosa+3 已知tana=-3,求sina+2cosa/cosa-3sina和sin^2a-sinacosa 已知(sina+cosa)/(sina-cosa)=2,则：(3sina+cosa)/(2sina+3cosa)=?sin^2a-2sinacosa+1=? 已知sina+cosa/sina-cosa=2,计算下列各式的值（1）3sina+cosa/2sina+3cosa(2)sin^a-2sinacosa+1. 已知tana=3,求下列各式的值 1.sina+cosa/sina-cosa 2.sina.cosa 3.sin^2 a+sina.cosa 已知sin=-3/5,那么(cosa+sina/cosa-sina)+(cosa-sina/cosa+sina)(a代表角, sinA=3sin(2π/3-A) SINA=?sinA=3sin(2π/3-A) SINA=?答案是-3√3cosA 为啥sina+cosa=√2sin(a+π/4) 若(sina+cosa)/(sina-cosa)=2,则sin(a-5派)*sin(3派/2-a)等于? 若(sina+cosa)/(sina-cosa)=2,则sin(a-5pai)*sin(3pai/2-a)等于? 已知tan(π-a)=2,求值：（1）2sin+2cosa/7sina+cosa（2）sina*cosa（3）4cosa^2+3sina^2 √2(cos^2a-sin^2a)/(sina-cosa)=-2√2/2,则cosa+sina=? (1-tana)/(1+tana)=2求(1)sina+cosa/(sina+2cosa) (2)sina-cosa(3)sin^2a-3cos^2a+1 已知tana=3,求①sina+cosa/2sina-cosa ②sin²a+sina·cosa+3cos²a tana=2,求2sina+cosa/sina-cosa和sin^2a-2Sinacosa+3cos^2a 若sina+cosa/sina-cosa=2,则4sin^2a-3sinacosa-5cos^2a= sin(a+kpai)=-2cos(a+kpai),k属于Z求(4sina-2cosa)/(5cosa+3sina)