Mathigon
Mathigon: Geometry: Polygons and Polyhedra: Polygons
This lesson focuses on polygons; a polygon is a closed, flat shape that has only straight sides. Polygons can have any number of sides and angles, but the sides cannot be curved.
Mathigon
Mathigon: Geometry: Triangles and Trigonometry: Properties of Triangles
This lesson focuses on the properties of triangles, a closed shape that has three sides, three vertices, and and three internal angles. There are different types of triangles such as a right triangle, obtuse, and acute based on the...
CK-12 Foundation
Ck 12: Interactive Geometry: 5.5 Geometry Software for Constructions
Use interactive geometry software to construct an equilateral triangle that maintains its shape even if you move its vertices.