sina +cosa=更号2sin(a+四分之派）吗

sina +cosa=更号2sin(a+四分之派）吗 已知(sina+cosa)/(sina-cosa)=3 则2sin'a+(sina-cosa)'=? sina=2cosa,求(1)3sina+2cosa(2)sin²a+sina×cosa+3 cos^2a-sin^2a=(cosa+sina)(cosa-sina)吗?求解 三角函数恒等式求证：cosa + sina / cosa - sina + cosa - sina / cosa + sina = cos＾2a - sin＾2a / 2 sina+cosa/sina-cosa=2 求sin^2a-2sinacosa+1 求证：cosa(cosa-cosb)+sina(sina-sinb)=2sin^2a-b/2 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 cosa/(sina+sin3a)=cosa/(2sin(2a)cosa)怎么来的啊 已知sin a+cos a=1/2 sina*cosa=?cos a/sina+sina/cosa=? tan a=2 ,2sina cosa=?(sin a )^2-sina cosa -2(cosa)^2=? 如果sina=2sin(a/2),则cosa= 怎么证明2sinA*cosA=sin(2A) 已知sin(pai-a)-2cosa=0若sina 为啥sina+cosa=√2sin(a+π/4)