A Point of Invariant Distancein an Equilateral Triangle
Equilateral triangles are the most symmetric triangles. The angle bisectors,
the altitudes, and the medians are all the same line segments. No other
triangle can boast this property. Their point of intersection is the center
of the inscribed and circumscribed circles, again a unique property. These
ought to be well-known properties. What is not well known is that if any
point is chosen in an equilateral triangle, the sum of the distances to the
sides of the triangle is constant. As a matter of fact, this sum is equal to
the length of the altitude of the triangle. Rather than simply present this
fact to your students, it would be advisable for them to experiment with
several points in an equilateral triangle. They should measure the distances
(perpendicular, of course) to each of the sides. They should notice that
the sum of the distances is the same for each selected point. Then by
measuring the length of the altitude of the triangle, they will find that
these distance sums are equal to the length of the altitude.