# Lines and Angles

Comprehension of lines and angles is critical in the study of geometry. Whether we know it or not, we see all sorts of angles on an everyday basis. The corners of a room, the way a ladder rests against a house, and the inclination of a hill all have angles that can be measured.

In order to continue our study of geometry, it will be necessary to learn about the different properties of lines, angles, and their measures. The sections below introduce the different classifications of angles (acute, obtuse, right, or straight) as well as some special properties of pairs of angles.

## Introduction to Angles

Main Lesson: Introduction to Angles

Learn about what angles are, how to name them, and the different classifications of angles.

## Pairs of Angles

Main Lesson: Pairs of Angles

Introduces complementary and supplementary angles as well as other special pairs of angles and helpful ways to identify them.

## Parallel and Perpendicular Lines in the Coordinate Plane

Main Lesson: Parallel and Perpendicular Lines in the Coordinate Plane

Utilizes algebraic equations in slope-intercept form to help study parallel and perpendicular lines in the coordinate plane.

## Angle Properties, Postulates, and Theorems

Main Lesson: Angle Properties, Postulates, and Theorems

Learn about the properties, postulates, and theorems of angles, in order to use them in a logic-based way for geometric proofs.