Angles are classified as either acute, obtuse, straight, or right. The measure of the degree of the angle determines the classification type. A right angle measures exactly 90o. An angle larger than 90o is an obtuse angle.
These resources are part of KET's Measurement and Geometry collection.
This video segment originally appeared in KET’s GED Connection series.
An angle is formed when two portions of a line share a common endpoint, or vertex. Angles are measured in degrees. The symbol for degrees is o. A right angle measures exactly 90o (90 degrees). The corner of a sheet of paper is a right angle. Right angles are formed when two lines are perpendicular. In a diagram, a right angle is marked with a square symbol. Right angles are very useful for solving geometric problems.
An angle larger than 90o is an obtuse angle.
Have learners look around the room for examples of right and obtuse angles. Use small adhesive-backed notes to temporarily label each of the angles.
Ask learners why they think right angles are used in construction more than any other angle.
Have learners draw a clock face and identify times when the hands on the clock form right and obtuse angles.
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