Trigonometry close trigonometryThe study of sides and angles in triangles. can be used to find a missing angle in a right-angled triangle when two sides are known. An understanding of the three ...

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 ...