I need to convert this rectangular equation into polar form:

I know that and . I've tried a little substitution but have not had a lot of success in simplifying it.

I also need to convert this polar equation into rectangular form:

I have a suspicion that is a useful tool, but I am having trouble with the conversion still. I used it to create this simplified equation in rectangular form:

Is this right? I simply substituted , subtracted and took the square root of everything. Is this correct?