Named for Plato, who theorized that the classical elements were made of these regular polyhedrons, three of the Platonic solids are composed of equilateral triangles: the tetrahedron, octahedron, and ...

Discusses the properties and types of triangles, explaining that a triangle is a closed figure with three sides and angles. It categorizes triangles into equilateral, isosceles, scalene, obtuse, right ...