Hello, I am trying to find the absolute maximum and/or minimum of

on the circle

I am stuck and would like some help if any1 can help me.

This is what I have so far,

setting the components equal to each other:

constraint:

I am having trouble solving for

I have 3 equations (including constraint) and 3 unknowns, It should work out. Can anyone help me? This is an algebra question, I feel like a moron.