Khan Academy: Triangles: Area of Diagonal Triangles of Rectangle Are Equal

Need an activity for teaching the Pythagorean Theorem? Geometry juniors apply the Pythagorean theorem to two triangles to determine a final calculation. 

This lecture explores finding the area of each of the triangles created by drawing two diagonal lines through a rectangle. It provides a detailed explanation of how to use a formula to solve the given problem. Tip: Use this for test...

Take a second look at triangles that are equal all the way around. The video reminds viewers what an equilateral triangle is and points out that the three angles are the same. Using the fact that equilateral triangles are also isosceles,...

This video tutorial [4:36] shows that the four triangles created by the diagonals of a rectangle all have the same area.

While the lesson focuses on right triangles, this activity offers a great way to practice the area of all triangles through an interactive webpage. The activity begins with the class taking a square paper and cutting in in half; can they...

This video tutorial explores finding the formula for the area of an equilateral triangle with side length of s.

Students explore a problem that requires then to figure out the area of an equilateral triangle inscribed in a circle using a little trigonometry.

In this video students explore summing an infinite geometric series to finally find the finite area of a Koch Snowflake.

This video [7:50] demonstrates how to determine the area a regular hexagon with side length of 2 sq. rt. 3 based on knowledge of 30-60-90 triangles and the area formula of a triangle.

In this video tutorial [11:06], the instructor shows how to construct a two-column proof using triangle congruence postulates to prove that two line segments are perpendicular.