Angle Relationships: Adjacent, Complementary, Supplementary, Linear Pair, and Vertical Angles.

You have a problem. It has two angles, one next to the other; they don't overlap, and they have algebraic expressions instead of numbers. How should you proceed? Do you equal both expressions? Or you add them equal to 90? Or 180 degrees?

This kind of problems are in the realm of angle relationships in geometry. In this lesson, you will have the opportunity to review basic angle definitions, and you will learn each one of these relationships in a dynamic way. Each relationship is presented with a set of examples, and after most of the examples; you will be presented with a suggested problem to solve, which will be graded instantly.

Lesson's Content

Lesson's Glossary

Angle
Geometric shape formed by two rays (initial and ending sides of the angle) that share a common endpoint called the vertex. You may name an angle using the vertex, or a point in each ray and the vertex label in the center.

Acute angle
An angle that is between 0 and 90 degrees.

Complement
Angle that together with the given angle adds up to 90 degrees.

Complementary angles
Two angles whose measures, when added together, equal 90 degrees.

Obtuse angle
An angle whose measure is greater than 90 but less than 180 degrees.

Supplement
Angle that together with the given angle adds up to 180 degrees.

Supplementary angles
Two angles whose measures, when added together, equal 180 degrees.

Vertical angles
Nonadjacent angles that are opposite by the vertex and are formed by two intersecting straight lines.

Interactive Geometric Applets: Relevant Theorems.

Interact with this applet to learn the basic definitions: Acute, Right, and Obtuse.

Drag point C within the shaded area to view different sets of complementary angles.

For this applet drag Point C to generate different sets of supplementary angles.

Drag point C, verify how these vertical angles are congruent.

Vocabulary Puzzle Interactive

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