First you should have a clear idea of what the thing you've drawn looks like:
I've taken the liberty to highlight the angles I find important for solving this problem.
Then you should take note that all angles within triangle DCP are the same, and that they add up to 180 degrees.
Also you should notice that
And lastly, you should notice that
One last point: never use a protractor(or any other tool for that matter) to solve a geometrical problem of any kind, unless the problem explicitly states that you should. The risk that you will end up with a faulty answer(which you actually did in this case) is huge.