8th Grade Math: Unit 1 - Parallel LInes and Transversals

Transversal

A Transversal is a line that crosses at least two other lines. The red line is the transversal in each example: Transversal crossing two lines. this Transversal crosses two parallel lines.

Linear Angles

A linear pair of angles is formed when two lines intersect. Two angles are said to be linear if they are adjacent angles formed by two intersecting lines. The measure of a straight angle is 180 degrees, so a linear pair of angles must add up to 180 degrees.

Similar Angles

If two angles of a triangle have measures equal to the measures of two angles of another triangle, then the triangles are similar. Corresponding sides of similar polygons are in proportion, and corresponding angles of similar polygons have the same measure

Parallel

In geometry, parallel lines are lines in a plane which do not meet; that is, two lines in a plane that do not intersect or touch each other at any point are said to be parallel.

Adjacent

Next to each other

Vertical

Opposite from each other

Consecutive Interior or (Same Side Interior) Angles

The pair of angles located inside the parallel lines (interior) and on the same transversal. These angles are supplementary (they have a sum of 180°)

Alternating Exterior Angles

The pairs of angles located inside the parallel lines (interior) and on opposite sides (alternate) of the transversal. These angles are congruent.

Alternating Interior Angles

The pairs of angles located inside the parallel lines (interior) and on opposite sides (alternate) of the transversal. These angles are congruent.

Corresponding Angles

These angles are in the same position in different intersections. If you translated one intersection to the other, the angles would correspond. They are congruent.

Vertical Angles

These angles are opposite of each other in the same intersections. They share the same vertex. They are congruent.

Supplementary

These angles have a sum of 180°. They form a straight line.

Complementary Angles

These angles have a sum of 90°. They form a right angle.

Triangle Sum Theorem

This Theorem states that the three interior angles of any triangle add up to 180 degrees.