Which of these functions has an average value of 000 on the interval [−π,π][-\pi, \pi][−π,π]?
f(x)=cos(x)f(x) = \cos(x)f(x)=cos(x)
f(x)=sin(x)f(x) = \sin(x)f(x)=sin(x)
f(x)=x2f(x) = x^2f(x)=x2
f(x)=exf(x) = e^xf(x)=ex