Honestly, I don’t take trigonometry, but I do know a little bit of the material that could help you.
Angle C is a square angle, meaning that it’s worth 90 degrees.
And it all the edges add up to 180, that means that the other two angles have to add up to ninety. It’s not 45 + 45, though, because angle B is smaller than angle A and that wouldn’t make any sense.
I know this wasn’t very helpful. Do you have a protractor lying around? Also, flipping the paper upside down (if needed) can sometimes give you a better mental picture.
