Angles in a parallelogram and a triangle

This is a set of three geometry videos dealing with angles.

First, showing that vertical angles are equal:



Next, finding out about the angles in a parallelogram. I start out with two parallel lines and a transversal (line that intersects them both). We explore the angles formed, which some of them are corresponding angles, some are vertical angles. I draw a new line, and get a parallelogram.



Lastly, here is a short and easy proof about the angles in a triangle.

Using a protractor

I've finally ventured into geometry topics with my latest video:



It shows how to use a protractor to measure angles. I show where the "base line" of the protractor is for three different protractors, and use it to find out the angle measure of different kinds of angles (including a reflex angle).