Rewrite in rectangular form: r=6 cos theta

I got (x-3)^2+y^2=6

2 answers

You almost had it.

r=6 cos Ø
recall that cosØ = x/r

r = 6x/r
r^2 = 6x , recall that r^2 = x^2 + y^2
x^2 + y^2 = 6x
x^2 - 6x + 9 + y^2 = 9
(x-3)^2 + y^2 = 9

check:
polar plot: http://www.wolframalpha.com/input/?i=polar+plot+r%3D6+cos+%C3%98
cartesian plot: http://www.wolframalpha.com/input/?i=plot+(x-3)%5E2+%2B+y%5E2+%3D+9
Thank you :)