Problem:

(h , k) = 4,11

Tangent Line: $\displaystyle f(x)= (-x/2)-2$

What I Want To Know:

How do you determine the radius?

Description:

I couldn't find what I was looking for in the book, so the past 20 minutes I've been trying to solve it with what I understand. The distance from the center point and the tangent line will be the shortest possible distance between the center point and any point on the line. The line segment I believe will be perpendicular so the slope of the line segment should be the negative reciprocal. Knowing this I would need to find out when the perpendicular line meets the center point and at what point the line touches the tangent line.