The figure shows a triangle ABC with
an interior point P and the altitudes h_{a}, h_{b},
and h_{c}. If p_{a}, p_{b}, and p_{c} are the
distances from P to the sides, prove that p_{a} / h_{a}
+ p_{b} / h_{b} + p_{c} / h_{c}
= 1. See also:
Artwork Problem 1072.
