#### Answer

$m = -\frac{h-c}{k-d}$

#### Work Step by Step

The tangent line is perpendicular to the radius. Thus, we first find the slope between the point and the radius:
$m= \frac{k-d}{h-c}$
The slope of the tangent line is the opposite reciprocal, so we find:
$m = -\frac{h-c}{k-d}$