### what is the problem with that integral ?

I try to integrate this:

sage: integrate(integrate(integrate(2*cos(z)*sin(atan((2*cos(y)-0.5+x)/(2*sin(y)))),y,0,pi/2),x,0,1),z,0,pi/2);

There is a problem :

"ECL says: In function ZEROP, the value of the only argument is
((RAT SIMP) -0.5 1.0)
which is not of the expected type NUMBER"

Could you help me please ?