2asin^2x-2根号3sinxcosx+a+b(a>0)定义域[0,二分之派]值域[-2,-1]求a,b

函数f(x)=2asin^2x-2根号3sinxcosx+a+b =a(1-cos2x)-根号3sin2x+a+b
=2a+b-(a*cos2x+根号3sin2x)=2a+b-根号下(3+a^2)sin(2x+α)
tanα=根号3/a,a>0 所以 tanα>0,取0