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?
, then and are parallel.
If two angles which form a straight angle are equal, what must their measures be?
is perpendicular to because and are both .
Under what circumstances are vertical angles equal?
Is there anything special about angles that add up to