A triangle is a polygon. It is a closed 3-sided shape made up of straight lines. The ‘tri-’ part of the word triangle means three. A triangle has 3 sides and 3 angles. Interior angles are the angles ...

Have you ever wondered why the cover of a manhole is nearly always round? Why isn’t it oval or square? Reuleaux curve based on an equilateral triangle. Reuleaux curves based on the pentagon (top) and ...