We show that plates having the shape of right triangles with equal hypotenuses which are free to swing about a perpendicular axis passing through the vertex of the right angle exhibit an isochronism similar to that of the simple pendulum, where the period depends on a single geometric parameter, namely the length of the string. In this case the parameter is the half-length of the hypotenuse and we show in addition that the center of oscillation is located exactly at the center of the opposite edge.
isochronism; right-angled triangles; compound pendulum
