These shapes are all regular polygons. A regular triangle is called an equilateral triangle. A regular quadrilateral is called a square. Irregular polygons are shapes that have sides and angles of ...

Each triangle has 180 ... where n is the number of sides In a regular polygon all the angles are equal. Each interior angle is calculated by dividing the sum of the interior angles by the ...

The ancient Greek mathematician Euclid proved in his Elements of Geometry that there are only five Platonic solids – the regular tetrahedron (four sides that are equilateral triangles), the cube (six ...