Answer:
Problem 1: 
Problem 2: 
Problem 3: 
Step-by-step explanation:
Problem 1:
So we are going to use the following to help us:



So if we make those substitution into the first equation we get:



Factor the
out:

The following is a Pythagorean Identity:
.
We will apply this identity now:

This implies:

We don't need both because both of include points with radius 4.
Problem 2:



Factoring out
from first two terms:

Apply the Pythagorean Identity I mentioned above from problem 1:


or if we factor out r:


r=0 is actually included in the other equation since when theta=0, r=0.
Problem 3:

