Is the theta in a projectile equation measured in degrees or radians?

The equations for projectiles shouldn't just have theta, they should have sin(theta) or cos(theta).

As long as you have your calculator set in the right mode, either will work when you evaluate sin or cosine.

Example: Say you have a projectile launched at 30 degrees above horizontal. In order to find the y velocity, you will have to calculate sin(30) with you calculator in degree mode. If instead you called this angle pi/6 (the same angle, just in radians), you could enter sin(pi/6) in your calculator in radians mode and get the same answer.