A triangle the lengths of the sides and the surface area of which are expressible by integers. Named after Heron (1st century A.D.), who studied triangles with side lengths $13,14,15$ and $5,12,13$, the surface areas of which are 84 and 30, respectively.
Comments
The Pythagorean triangles are special cases (cf. Pythagorean numbers).
Heron triangle. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Heron_triangle&oldid=32895