PARALLEL LINES AND TRANSVERSALS SECTIONS

CORRESPONDING ANGLES POSTULATE Two lines cut by a transversal are parallel if and only if the pairs of corresponding angles are congruent.

ALTERNATE INTERIOR ANGLES THEOREM Two lines cut by a transversal are parallel if and only if the pairs of alternate interior angles are congruent.

ALTERNATE EXTERIOR ANGLES THEOREM Two lines but by a transversal are parallel if and only if the pairs of alternate exterior angles are congruent.

CONSECUTIVE INTERIOR ANGLES THEOREM Two lines cut by a transversal are parallel if and only if the pairs of consecutive interior angles are supplementary.

TRANSITIVE PROPERTY OF PARALLEL LINES If two lines are parallel to the same line, then they are parallel to each other.

EXAMPLE Find each numbered angle.

EXAMPLE Find the value of x.

EXAMPLE Find the value of x. The picture may not be drawn to scale. (3x + 5) o (7x – 15) o

LINEAR PAIR PERPENDICULAR THEOREM If two lines intersect to form a linear pair of congruent angles, then the lines are perpendicular.

PERPENDICULAR TRANSVERSAL THEOREM If a transversal is perpendicular to one of two parallel lines, then it is perpendicular to the other.

LINES PERPENDICULAR TO A TRANSVERSAL THEOREM In a plane, if two lines are perpendicular to the same line, then they are parallel to each other.

ASSIGNMENT p. 142: 3-8, 13-18, p. 153: 17-23