3.5 Parallel Line Properties

What We Have Learned So Far I

� Two lines cut by a transversal are parallel if and only if the following angle pairs are congruent:� Corresponding angles� Alternate Interior angles� Alternate Exterior Angles

� “Congruent” means you can set their measures equal to each other

<1 ≅ <2 m<1 = m<2

What We Have Learned So Far II

� Two lines cut by a transversal are parallel if and only if the following angle pairs are supplements:� Consecutive Interior angles� Consecutive Exterior Angles

� “Supplements” add to 180

<1 and <2 are supplements if and only if m<1 + m<2 = 180

Transitive Property of Parallel Lines

� If 2 lines are parallel to the same line, then they are parallel to each other.

� If i || j and j || k then i || k

k

ji

Perpendicular Transversals

� In a plane, if 2 lines are perpendicular to the same line, then they are parallel to each other.

� If m ┴ p and n ┴ p then m || nm n

p

Practice

� TB p160: 8-24, 43-52

Practice

� TB p160: 8-24, 43-52