Khan Academy on a Stick

Triangle area proofs

Proving that the area of any triangle is 1/2 b x h

Perimeter and area of triangles

Perimeter and area: the basics
Triangle area proofs
Interesting perimeter and area problems
Area of diagonal generated triangles of rectangle are equal
Area of an equilateral triangle
Area of shaded region made from equilateral triangles
Challenging perimeter problem

If the above player doesn't work, try this direct link.

All Khan Academy content is available for free at www.khanacademy.org.
This collection was created November 2014.