Compare your answers.

Determine all the unknown angles in the diagram.

 

 

For further information about finding angle measures formed by a transversal of parallel lines see pp. 76–77 of of Principles of Mathematics 11.

 

When a transversal crosses a set of parallel lines, a number of angles are produced. Pairs of opposite, corresponding, alternate interior, and alternate exterior angles are all equal when this occurs. Knowing these relationships means that you will often be able to determine a number of unknown angle measures from a diagram involving parallel lines even if very little information is given. In the next lesson, you will begin to explore the angle relationships of polygons.