# Finding radius from just a point

• March 22nd 2010, 07:02 PM
florx
Finding radius from just a point
http://i43.tinypic.com/dykvwl.jpg

The problem says to find the missing variables on the circle. That includes r, theta, and s. So what would be the first step to figuring out this problem? And how would I find the radius with only point given as (7,4)?

Thanks.
• March 22nd 2010, 07:12 PM
Stroodle
$r^2=7^2+4^2$

and

$\theta=tan^{-1}\left (\frac{4}{7}\right )$

and for $s$ remember the circumference is $2\pi r$ and there are 360 degrees in a circle.
• March 22nd 2010, 07:14 PM
florx
Thank you so much Stroodle for your help!