Can someone point out where I am going wrong in this problem?

Three forces are applied to an object, as indicated in the drawing. Force 1 has a magnitude of 33.0 newtons (33.0 N) and is directed 30.0° to the left of the +yaxis. Force 2 has a magnitude of 16.0 N and points along the +xaxis. What must be the magnitude and direction (specified by the angleθin the drawing) of the third force 3 such that the vector sum of the three forces is 0 N? magnitude28.6 Nθ2°

The only thing I need to do is find theta. I thought it would work by doing tan^-1(28.6) but that gave me 88 degrees and it didn't work. Suggestions?

Thanks,

juventinoalex