Question

已知sina+mcosa=n,求msina-cosa的值(实数m,n满足1+m^2>n^2)

Answer 1

(sina+mcosa)^2+(msina-cosa)^2=(1+m^2)

∵sina+mcosa=n

∴ msina-cosa=√(1+m^2-n^2)

说明：题目中的1+m^2>n^2是为了保证根号有意义才给的条件