1. Differentiate intersecting, parallel, and skew lines; 2. Classify pairs of angles generated whenever two lines are cut by a transversal; and 3. Cite examples of parallel lines in real life.

Are the horizontal lines parallel?

are planes that do not intersect M N

p q are coplanar and do not intersect R

are not coplanar and do not intersect M N a b

Theorem: If two parallel planes are cut by a third plane, the lines of intersection are parallel. A B C P S R D

a line that intersects two coplanar lines in two different points a b c

Corresponding angles are two nonadjacent angles on the same side of the transversal such that one is an exterior angle and the other is an interior angle. a b c

Interior angles: Exterior angles: 3, 4, 5, and 6 1, 2, 7, and 8 a b c

Alternate interior angles are two nonadjacent interior angles on opposite sides of the transversal.  3 &  5,  4 &  6 a b c

Alternate exterior angles are two nonadjacent exterior angles on opposite sides of the transversal.  1 &  7,  2 &  8 a b c

Same-side interior angles are two interior angles on the same side of the transversal. a b c  3 &  6,  4 &  5

Same-side Exterior angles are two exterior angles on the same side of the transversal. a b c  1 &  8,  2 &  7

Identify each angle pair as alternate interior, alternate exterior, same-side interior, same-side exterior, corresponding, or none of these. Try these

 5 and   6 and  7 3.  2 and  9

 9 and   5 and  8 6.  1 and  14