How would I calculate the degree measure of a number like tan(45) in Java?

In case the title was confusing, here is what I mean. When I use the code Math.tan(45); to return a number, I can't use Math.atan(Math.tan(45)); to return 45. I can't just make it simply return 45, because I want it to be dynamic.

How would I return the degree measure of a tangent, sine, or cosine?