Geometric Properties

Everyone knows that opposite sides of a parallelogram are congruent, but can you prove it? Challenge pupils to use triangle congruence to prove properties of quadrilaterals. Learners complete formal two-column proofs before moving on to...

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

Isn't paper pushing supposed to be boring? Learners attempt a paper-pushing puzzle to develop ideas about angles inscribed on a diameter of a circle. Learners then formalize Thales' theorem and use geometric properties to develop a proof...

If two sets of angles are equal, the third set is too. An informative portion of a playlist on geometry develops the Third Angle Theorem for triangles. Using the theorem, the presenter shows how to determine the measure of missing angles...

The Pythagorean Theorem works for something other than right triangles; show your class all it can do. Using information from the Pythagorean Theorem, the video shows how to determine whether a triangle is an acute or obtuse triangle....

In this video, Sal introduces the Pythagorean Theorem to viewers, crossing into the realm of geometry. He uses several examples, including right triangles, to illustrate the applications and uses of the Pythagorean Theorem.

As the fourth part of a series on the Pythagorean Theorem, Sal continues an exploration of the ways to calculate the length of sides of a right triangle using algebra. He also used this theorem to solve problems involving a right...

This lecture, the second in a series on the Pythagorean Theorem, delves into more complex problems. Primarily, it examines the process of finding the value of a hypotenuse. It is beneficial because the example problem is one in which the...

Need to find the length of a side of a right triangle? Just use the Pythagorean Theorem! Follow along as the tutor defines the Theorem, explains how it works, then uses it to determine the missing length of a right triangle. 

Middle and high schoolers construct a triangle using Cabri Jr. They construct squares on each of the legs and hypotenuse of the triangle. Pupils show that the area of the squares on the leg equal the area of the square on the hypotenuse.