Alternate Exterior Angles
When two lines are crossed by another line (which is called the Transversal), the pairs of angles on opposite sides of the transversal but outside the two lines are called Alternate Exterior Angles.
Construct a Square
Transforming a Triangle
Interior Angles of a Triangle And Supplementary Angles
Points, Lines, and Planes Applet
Fierbach Circle and Oiler line 3
Sequences and Series