Angles
Definitions
Two angles sharing a common ray are called adjacent.
Two adjacent angles lying along a line are called supplementary angles.
If two supplementary angles are equal they are right angles.
Two lines are intersected by a third line. The angles α and β are corresponding angles.
Two lines are intersected by a third line. The angles α and β are alternate angles.
α and β are vertical angles.
α is an exterior angle to the triangle ΔABC.
Exercises
Make a line a through the points A and B, and a line b through the points C and D. Enter the point of intersection E and the angle α. Place a point F on the line b.
Exercise 1
Make an angle β at the point F equal to α , and such that β becomes an alternate angle when a new line is drawn. What can you say about the line a and the new line?
Exercise 2
Make an angle β at the point F equal to α , and such that β becomes a corresponding angle when a new line is drawn. What can you say about the line a and the new line?
by Malin Christersson under a Creative Commons Attribution-Noncommercial-Share Alike 2.5 Sweden License
