sina=x sinb=y sin(a+b)=?
问题描述：
sina=x sinb=y sin(a+b)=?
答
sin(a+b)=sina*cosb+cosa*sinb=x根号（1-y^2）+y根号（1-x^2）
答
sina = x、sinb = y
cosa = ±√(1 - x^2)
cosb = ±√(1 - y^2)
sin(a + b)
= sina*cosb + cosa*sinb
= ±[√(1 - y^2)]*x ±[√(1 - x^2)]*y