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: 1.11 Surface Area and Nets
Explore surface areas and nets with 2D and 3D shapes.