### Home > GC > Chapter 6 > Lesson 6.2.2 > Problem 6-50

6-50.

**Examine** the diagram at right. Based on the information below, what statement can you make about the relationships between the lines? Be sure to **justify** each conclusion. Remember: each part below is a separate problem.

When do alternate interior angles have equal measures?

If

, thenandare parallel.

If two angles which form a straight angle are congruent, what must their measures be?

is perpendicular tobecauseand are both.

Under what circumstances are vertical angles congruent?

Is there anything special about angles that add up to

?