#### Answer

The graph is composed of two perpendicular lines passing through the origin with slopes $1$ and $-1$.

#### Work Step by Step

Conversion of polar coordinates and Cartesian coordinates are as follows:
a)$r^2=x^2+y^2 \implies r=\sqrt {x^2+y^2}$
b) $\tan \theta =\dfrac{y}{x} \implies \theta =\tan^{-1} (\dfrac{y}{x})$
c) $x=r \cos \theta$
d) $y=r \sin \theta$
Here, we have $r^2 \cos^2 \theta =r^2 \sin^2 \theta$
Therefore, our Cartesian equation is $x^2=y^2 \implies x=\pm y$ or, $y=\pm x$
This shows that the graph is composed of two perpendicular lines passing through the origin with slopes $1$ and $-1$.