Is the E Field Direction Downward for a Ring with Continuous Polarization?

[O.J.]

a ring whose upper half is continuously + and lower half is continuously - at a point P a distance d from the centre. Now our instructer solved it for us pointing that the direction of the field is downwards. but I am not convinced, because although the sine is contant, each time to move dTHETA u have a component in the z direction, while the magnitude we found was assigned a y direction only...:(:(

 

[O.J.]

any ideas?