Math Help - Finding radius from just a point

1. Finding radius from just a point

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.

2. $r^2=7^2+4^2$

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.

3. Thank you so much Stroodle for your help!