# Convert the Cartesian equation to the polar equation

## Homework Statement

Replace the Cartesian equation with an equivalent polar equation.
##x^2 + (y - 18)^2 = 324##
a)##r = 36 sin θ##
b)##r^2 = 36 cos θ##
c)##r = 18 sin θ##
d)##r = 36 cos θ##

## Homework Equations

##x= r cos \theta ##
##y= r sin \theta ##
##x^2 + y^2 = r^2 ##

## The Attempt at a Solution

##x^2 + (y - 18)^2 = 324##
##x^2 + y^2 - 2*18*y + 18^2 = 324 ##
##x^2 + y^2 - 36 y =0##
##r^2 = 36 y##
Divide by r :
##r = 36 r sin \theta##
So , the answer is (a) .Right ?