Geometry Basics: Points, Lines, and Angles

Geometry Basics

• Geometry is a branch of mathematics that deals with shapes, measurements, and relationships of points, lines, and angles.

Points

• A point is an exact location in space with no length or width.
• A point has zero dimensions.
• Points are labeled with a single capital letter.
• In coordinate geometry, points can be plotted on a coordinate plane and located by coordinates.
• The coordinate of a point is written as a point (e.g., (3, 2)).

Lines

• A line is a straight set of points that continue in opposite directions forever.
• A line has length, but no width, making it one-dimensional.
• There are different kinds of lines in geometry, including:
  • Horizontal lines: move from left to right.
  • Vertical lines: move up and down.
  • Perpendicular lines: intersect at a right angle.
  • Parallel lines: never get closer or farther away from each other.

Line Segments

• A line segment is part of a line with two endpoints.
• A line segment does not go on forever, but has a specific beginning and ending point.
• Line segments are usually labeled with two points at the endpoints.

Rays

• A ray is part of a line, but it differs from a line segment.
• A ray has a starting point, but it extends from that starting point in one direction forever.
• A ray is identified by its starting point and another point it passes through.

Angles

• An angle is created by two rays that share the same starting point (vertex).
• An angle is measured by the distance between its rays in degrees.
• Angles can be identified or named by their vertex or by three points on the angle.
• There are different types of angles, including:
  • Right angle: exactly 90 degrees.
  • Acute angle: less than 90 degrees.
  • Straight angle: exactly 180 degrees.
  • Obtuse angle: greater than 90 degrees, but less than 180 degrees.
  • Reflex angle: between 180 degrees and 360 degrees.

Learn the fundamental concepts of geometry, including points, lines, and angles. Understand the definitions and importance of these core concepts in mathematics.