Answer
(a) $ x^2+y^2=25$
(b) circle, center $(0,0)$, radius$=5$. See graph.
Work Step by Step
(a) Use the relations $r^2=x^2+y^2, r\ sin\theta=y, r\cos\theta=x$, we have $r=5\Longrightarrow r^2=25 \Longrightarrow x^2+y^2=25$
(b) We can identify the equation as a circle with center $(0,0)$, radius$=5$ (rectangular system). See graph.
