Length of Tangent Segment in Circles

In a circle with a radius of $r$, two tangent lines are drawn from an external point to the circle. The distance from the external point to the center of the circle is $d$. If the distance between the two points of tangency is $L$, what is the relationship between $L$, $r$, and $d$?

Recall the geometric property that states that the line segment connecting the external point to the center of the circle and the line segments connecting the external point to the points of tangency form a right triangle.