The Monthly publishes articles, as well as notes and other features, about mathematics and the profession. Its readers span a broad spectrum of mathematical interests, and include professional ...

The six intersection points of a triangle’s non-parallel altitudes and perpendicular bisectors are the vertices of two congruent minor periambic triangles which are inversely similar to the original.

A quadrilateral is a four-sided shape. It could be a square, rectangle, kite, rhombus, parallelogram or trapezium. For any quadrilateral, the angles of the four corners add up to \(360^\circ\). The ...