Originally Posted by

**Skinner** Hello everyone:

I'm reviewing for a test, and I got some questions regarding polar coordinates:

Question one:

Show that the point $\displaystyle (2, 3\pi/4) $ lies on the curve $\displaystyle r = 2 sin2\theta $

Specifically, when you simply "plug in" the $\displaystyle r $ and $\displaystyle \theta $, it gives you a false equality. I know that there are multiple ways to express the point $\displaystyle (2, 3\pi/4) $, and that apparently you must replace this point with an equivalent point in order to make the equality work. What exactly must I do to make this work?

Question two:

Find the intersections of this pair of curves:

$\displaystyle r = 1 + cos\theta $ and $\displaystyle r = 1 - cos\theta $

Thanks!