How exactly can I find the value of $C_{1}$ so that f is a joint density function?
$$f(r,\theta)= \begin{cases} C_{1}(1-r^{2}), & \text{if} (r,\theta)∈ R\\ 0, & \text{otherwise} \end{cases}$$
Where R is the region inside of r = 2+4cosθ (which includes the inner loop)