# Can someone help me with these two?

• July 14th 2008, 05:07 PM
Dave53
Can someone help me with these two?
Change the following polar equation to rectangular form.
r=cotΘ
Find a polar equation of the conic with focus at the pole and the given eccentricity and directrix.
e=3/2,ysinΘ=1
Thanks again for the help!
Dave
• July 14th 2008, 05:43 PM
topsquark
Quote:

Originally Posted by Dave53
Change the following polar equation to rectangular form.
r=cotΘ

$r = cot(\theta)$

$r = \frac{cos(\theta)}{sin(\theta)}$

$r~sin(\theta) = cos(\theta)$

Now,
$y = r~sin(\theta)$
and
$x = r~cos(\theta) \implies cos(\theta) = \frac{x}{r} = \frac{x}{\sqrt{x^2 + y^2}}$

So
$y = \frac{x}{\sqrt{x^2 + y^2}}$

-Dan