首先f'(x)=1+cosx,在(-π/2,π/2)是单调递增的.
f(1)=1+sin1,f(2)=f(π-2)=π-2+sin(π-2),f(3)=f(π-3)=π-3+sin(π-3)
π-3《1《π-2
所以f(3)