Let X and Y denote the coordinates of a point uniformly chosen in the circle of radius

Question:

Let X and Y denote the coordinates of a point uniformly chosen in the circle of radius 1 centered at the origin. That is, their joint density is
f(x, y) = 1/πx2 + y2 ≤ 1
Find the joint density function of the polar coordinates
R = (X2 + Y2)1/2 and Θ = tan−1 Y/X.