f(x)=a*b=√3sinxcosx+cos^2x=√3/2sin2x+1/2cos2x+1/2=sin(2x+π/6)+1/2x∈［－π/6，π/3］2x+π/6∈［－π/6，5π/6］f(x)=sin(2x+π/6)+1/2在［－π/6，5π/6］上值域为:[0,3/2]当x=－π/12时,f(x)有最小值=0当x=π/6时,f(x)有最大值=3/2
