How do I calculate this integral?

Hi.

I have defined a function "norma" that calculates the normal vector in a point "r" in a given surface:

norma:=proc(l,r) local nu;

if r[1]>= l/2 then nu:=[r[1]-l/2,r[2]];

elif r[1]<=-l/2 then nu:=[r[1]+l/2,r[2]];

...

Now I need to calculate an integral using this function varyign the parameter "r" but I get this error message:

> int(norma(l,[cos(x), sin(x)]), x = -1.5768 .. -.5638);
Error, (in norma) cannot determine if this expression is true or false: [(1/2)*cos(x), (1/2)*sin(x)] <= 2

Is there another way to calculate this integral? Thanks.