A couple of hints that should be enough if you think about them carefully.

arctangent documentation

Mathematica, and sometimes WolframAlpha, work in radians where 360 degrees is 2*pi, 180 degrees is pi, 90 degrees is pi/2, etc. You might try a few simple WolframAlpha queries and see if you can understand whether it is using radians or degrees. If in a particular problem you append "in degrees" to the end of your question, not including the quotes, then that is sometimes enough to let WolframAlpha know that you want an answer expressed in degrees instead of in radians.

Together those should be enough.