Measuring and Classifying Angles

Pre-Algebra · Axiom Academy

EXAMPLE Measuring and Classifying Angles Estimate, measure, and classify an angle from its diagram — then find its complement and supplement. The angle below is formed by two rays meeting at the vertex B . Estimate its measure, confirm it with a protractor, classify it by type, and then find its complement and its supplement . Nice work! You estimated , confirmed it with a protractor as , classified it, and found both partner angles. Estimate first: a rough estimate (here, near ) catches gross measuring mistakes before you trust the protractor. Classify by measure: acute is to , right is exactly , obtuse is to , straight is exactly . Complement: two angles that add to . For that is . Only acute angles have a complement. Supplement: two angles that add to . For that is . Every angle under has one. The same three moves — measure, classify, then find the complement and supplement — work for any angle you read off a diagram.

This is the written version of the interactive lesson above. See the full Pre-Algebra course.