## 3.1 Lines and Angles

**Parallel lines: coplanar lines that do not intersect.**

Perpendicular lines: lines that intersect at 90 degrees

Skew lines: not parallel, not coplanar, and do not intersect

Parallel planes: planes that do not intersect

Transversal: a line that intersects two coplanar lines at two different points

Corresponding angles: angles that lie on the same side of the transversal and on the same sides of the two lines

Alternate interior angles: nonadjacent angles that lie on opposite sides of the transversal and between the two lines

Alternate exterior angles: lie on opposite sides of the transversal, and on the outsides of the two lines

Same-side interior angles: lie on the same side of the transversal and between the two lines

Perpendicular lines: lines that intersect at 90 degrees

Skew lines: not parallel, not coplanar, and do not intersect

Parallel planes: planes that do not intersect

Transversal: a line that intersects two coplanar lines at two different points

Corresponding angles: angles that lie on the same side of the transversal and on the same sides of the two lines

Alternate interior angles: nonadjacent angles that lie on opposite sides of the transversal and between the two lines

Alternate exterior angles: lie on opposite sides of the transversal, and on the outsides of the two lines

Same-side interior angles: lie on the same side of the transversal and between the two lines