Triangles (Jump to: Lecture  Video )
Triangle 
A triangle is a shape made up of three line segments which intersect at their endpoints.

The three angles of any triangle add up to 180 degrees.
Triangles can be classified as Right Triangles, Acute Triangles, or Obtuse Triangles.
Right Triangle 
A Right Triangle is a triangle with one right angle.

Acute Triangle 
An Acute Triangle is a triangle with all acute angles.

Obtuse Triangle 
An Obtuse Triangle is a triangle with one obtuse angle.

Triangles can also be classified by the length of their sides. There are Equilateral Triangles, Isoceles Triangles, and Scelene Triangles.
Equilateral Triangle 
An Equilateral Triangle is a triangle with all thee sides equal.

Isoceles Triangle 
An Isoceles Triangle is a triangle with two equal sides.

Scalene Triangle 
A Scalene Triangle is a triangle with no equal sides.
