Show it can all be proved. Scholars learn the converses of the properties of parallel lines. Using the converses, pupils determine which lines are parallel based on angle measurements and practice using a flow proof to show that two...

Look at proportionality from a parallel perspective. A section of an expansive geometry playlist introduces the Triangle Proportionality Theorem. Using the theorem, the video shows how to determine missing measurements in triangles.

If you add the value of the three interior angles in a triangle will it equal 180 degrees? Yes it will. The instructor illustrates and proves the Triangle Sum Theorem. Follow closely as she explains her proof.

Using a similar method that he used to prove the sum of angles formula for sine, Sal shows the proof the cosine sum of angles formula, cos (a+ b) = cos (a) cos (b) - sin (a) sin (b). This proof also uses the SOH-CAH-TOA model and some...

Sal proves the sum of angles formula for sine, sin (a+ b) = cos (a) sin (b) + sin (a) cos (b), through a clear but rather non-intuitive proof. The proof is interesting as it uses the SOH-CAH-TOA model and requires one to recall some...

Using a similar method that he used to prove the sum of angles formula for sine, Sal shows the proof of the cosine sum of angles formula, cos (a+ b) = cos (a) cos (b) - sin (a) sin (b). This proof also uses the SOH-CAH-TOA model and some...

This lesson [5:22] will demonstrate how to prove lines parallel with the converse of the corresponding angles postulate. It is 6 of 6 in the series titled "Corresponding Angles Converse."

This lesson will demonstrate how to prove lines parallel with the converse of the corresponding angles postulate. It is 1 of 6 in the series titled "Corresponding Angles Converse." [2:37]

This lesson [3:41] will demonstrate how to prove lines parallel with the converse of the corresponding angles postulate. It is 3 of 6 in the series titled "Corresponding Angles Converse."

This lesson [3:57] will demonstrate how to prove lines parallel with the converse of the corresponding angles postulate. It is 4 of 6 in the series titled "Corresponding Angles Converse."

This lesson [3:29] will demonstrate how to prove lines parallel with the converse of the corresponding angles postulate. It is 5 of 6 in the series titled "Corresponding Angles Converse."

Proving that vertical angles are equal

This video tutorial demonstrates solutions to problems #51-55 of the California Geometry released state test questions. Problems address proving and using the Pythagorean theorem and compass constructions. [12:35]

Demonstrates how to prove that the opposite sides of a parallelogram are congruent based on knowledge of the special angles created when parallel lines are cut by a transversal and the triangle congruency postulates. [8:30]

This video tutorial demonstrates how to prove that the opposite angles of a parallelogram are congruent based on knowledge of the special angles created when parallel lines are cut by a transversal. [4:08]

Demonstrates how to prove that the diagonals of a parallelogram bisect each other based on knowledge of the special angles created when parallel lines are cut by a transversal and the triangle congruency postulates. [9:06]

This video tutorial describes and provides an example for proving two lines are parallel with the converse of consecutive-interior angles theorem. Students can check their understanding with an assessment.