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Postulate 3.1 "Corresponding Angles Postulate" (HW Postulate 10)

If 2 parallel lines are cut by a transversal, then corresponding angles are congruent.

Theorem 3.1 "Alternate Interior Angles Theorem" (HW Theorem 3-2)

If 2 parallel lines are cut by a transversal, then alternate interior angles are congruent.

Theorem 3.2 "Consecutive Interior Angles Theorem" (HW Theorem 3-3)

If 2 parallel lines are cut by a transversal, then consecutive interior angles are supplementary.

Theorem 3.3 "Alternate Exterior Angles Theorem"

If 2 parallel lines are cut by a transversal, then alternate exterior angles are congruent.

Theorem 3.4 "Perpendicular Transversal Theorem" (HW Theorem 3-4)

If a transversal is perpendicular to one of 2 parallel lines, then it is perpendicular to the other one also.

Postulate 3.4 (HW Postulate 11)

If 2 lines are cut by a transversal, and corresponding angles are congruent, then the lines are parallel. (converse Corresponding Angles Postulate)

Theorem 3.7 (HW Theorem 3-5)

If 2 lines are cut by a transversal, and alternate interior angles are congruent, then the lines are parallel. (converse Alternate Interior Angles Theorem)

Theorem 3.6 (HW Theorem 3- 6)

If 2 lines are cut by a transversal and consecutive interior angles are supplementary, then the lines are parallel. (converse Consecutive Interior Angles Theorem)

Theorem 3.8 (HW Theorem 3-7)

In a plane, 2 lines perpendicular to the same line are parallel. (converse Perpendicular Transversal Theorem)

Theorem 3.5

If two lines are cut by a transversal and alternate exterior angles are congruent, then the lines are parallel. (converse Alternate Exterior Angles Theorem)

Postulate 3.5 "Parallel Postulate" (HW Theorem 3-8)

Through a point outside a line, there is exactly one line parallel to the given line.

HW Theorem 3-10

2 lines parallel to a third line are parallel to each other.

Postulate 3.2 (HW Theorem 13-3)

2 non-vertical lines are parallel if and only if their slopes are equal.

Postulate 3.3

2 non-vertical lines are perpendicular if and only if their slopes are opposite reciprocals.

Point-Slope Form

(y-y₁)= m(x-x₁)

Standard Form

Ax+By=C

Point-Line Distance Formula

d=|ax₁+by₁+c|/√a²+b²