The Basics: Points, Lines, and Angles

Geometry starts with the smallest pieces. A point is just a location, no size, drawn as a dot. A line goes straight forever in both directions. A plane is a flat surface that goes forever in every direction, like an endless field.

Segments and rays

• ●A segment is a piece of a line with two endpoints, like the yard line between two markers.
• ●A ray starts at one point and goes forever in one direction, like a flashlight beam.

Angle types

• ●Acute angle: less than 90 degrees (sharp).
• ●Right angle: exactly 90 degrees (a perfect corner).
• ●Obtuse angle: more than 90 but less than 180 degrees (wide open).
• ●Straight angle: exactly 180 degrees (a flat line).

Example: if one angle is 30 degrees, its complement is 60 degrees (30 + 60 = 90) and its supplement is 150 degrees (30 + 150 = 180).