已知函数y=-cos^2x+asinx+1/2(a为常数,且a

问题描述:

已知函数y=-cos^2x+asinx+1/2(a为常数,且a

y=sin^2x+asinx-1/2
=(sinx+a/2)^2-1/2-a^2/4.
又a