Find an Equivalent Equation in Rectangular Coordinates $$\mathbf { r } = \cos \theta$$

Multiple Choice

Find an equivalent equation in rectangular coordinates.
- $$\mathbf { r } = \cos \theta$$

A) $x ^ { 2 } + y ^ { 2 } = x$
B) $( x + y ) ^ { 2 } = y$
C) $( x + y ) ^ { 2 } = x$
D) $x ^ { 2 } + y ^ { 2 } = y$