Which of the following functions is odd?
f(x)=x2+xf(x) = x^2 + xf(x)=x2+x
f(x)=sin(x)+xf(x) = \sin(x) + xf(x)=sin(x)+x
f(x)=cos(x)f(x) = \cos(x)f(x)=cos(x)
f(x)=x2+1f(x) = x^2 + 1f(x)=x2+1