Lines & Angles

Parallel Lines Coplanar lines that don’t intersect

Symbol for parallel

We most often show lines or segments are parallel by marking them with arrowheads.

Skew lines Lines that don’t intersect because they are in different planes

Parallel planes Planes that do not intersect

Transversal . A line that cuts across. other lines  Transversal  A line that cuts across other lines  Intersects 2 or more coplanar lines

Transversals divide two lines into regions we call interior and exterior.

We often refer to specific types of angles formed by transversals.

Corresponding Angles . Same side of transversal  Corresponding Angles  Same side of transversal  Corresponding positions (e.g.: above or below the lines)

Which pairs of angles are corresponding angles?

Which pairs of angles are corresponding angles

Alternate interior angles . Opposite sides of. transversal  Alternate interior angles  Opposite sides of transversal  Between the lines

Which pairs of angles are alternate interior angles?

Which pairs of angles are alternate interior angles? 2 & 5 3 & 6

Same-Side Interior Angles (also called “consecutive interior angles”)  Same side of transversal  Between the lines

Which pairs of angles are same-side interior angles?

Which pairs of angles are same-side interior angles? 2 & 6 3 & 5

Alternate exterior angles . Opposite side of. transversal  Alternate exterior angles  Opposite side of transversal  Outside the lines

Which pairs of angles are alternate exterior angles?

Which pairs of angles are alternate exterior angles? 1 & 7 4 & 8

Identify the pairs of special angles.

Remember

. Parallel lines . Skew lines . Parallel planes . Transversal   Parallel lines  Skew lines  Parallel planes  Transversal  Interior/Exterior  Corresponding s  Alternate interior s  Same-side interior s  Alternate exterior s