Im currently studying for an exam which frankly is way over my head, so I want to see who can help me, right now with this particular problem. I need not only the solution but how to solve and how to apply it to other situations. Thank you and have a good day.

Denoted by D, the domain {(x,y)}| x>=0, y>=0}

Assume a circle C contained in D touches parabola y=(1/2)x^2 at the point (2,2) and also touches the x-axis. Find the radius of C.

Please show all steps and explain them to me as I might need to apply this to other problems.