LINE & ANGLES CHEAT SHEET
Geometry starts with undefined terms - points, lines, and planes. A point shows a location (represented by a dot), while a line extends infinitely in two directions. A plane is a flat surface that extends without end in all directions, like an infinite sheet of paper.
Lines have variations: line segments have two endpoints, while rays have one endpoint and extend infinitely in one direction. When lines meet, they create angles, measured in degrees. Perpendicular lines meet at exactly 90° angles, forming a cross shape, while parallel lines never intersect at all.
Angles have special relationships when they appear together. Complementary angles add up to 90°, while supplementary angles sum to 180°. A linear pair forms a straight line (180°), and vertical angles created by intersecting lines are always equal to each other.
💡 Remember: When parallel lines are cut by a transversal (a line crossing through them), eight angles form with special relationships. Corresponding angles are in the same position and are equal, while alternate interior angles are between the parallel lines and equal.
When working with these concepts, look for patterns in angle relationships. Same-side interior angles are supplementary (add to 180°), and alternate exterior angles are congruent (equal). Understanding these relationships helps solve geometry problems efficiently!