I have a problem that seems easy enough but i cant seem to find x and y

Problem: find a Parametrization for the graph of the function

Starting at (3,9) and moving towards the origin,using angle

in the accompanying figure as a parameter.

I drew out the graph and took a picture of it and i will include it.

I think i use

Im not sure how to finish solving for x then to solve for y?

Im not sure if i need to find since the slop comes out as zero?

Thank you..