# Math Help - Average Value of a Function

1. ## Average Value of a Function

The average value of a function f(x)=cos(1/2x) on the closed interval [-4,0] is
A) -1/2 sin(2)
B) -1/4 sin (2)
C) 1/2 cos (2)
D) 1/4 sin (2)
E) 1/2 sin (2)

I don't know what I'm doing wrong but I always end up with 1/2 sin(-2)
$\int_{ - 4}^0 {\cos \left( {\frac{x}