# Geometry Part 6: Angles and Lines

by C. Elkins, OK Math and Reading Lady

When working with students on geometry lessons involving angles and lines, I notice many misconceptions. So . . . I thought I would share them with you on this post. Some activity ideas and freebies are located at the end of this post.

Right Angles:

1. Students can only see the 90° angle if it is presented in the direction as a capital L.
• Try turning the angles in different positions.
• It is still considered a “right” angle even though it is turned to the left, up, or down.
2. Students are told if they can draw a square inside the angle, then it is a right angle. So if it looks “squarish” to them, they think it’s a right angle.
• Show them how to put the square corner of a piece of paper or index card into the angle to check. Take time to have them practice – don’t assume they know how. Acute Angles (angles less than 90°):

1. Students often can’t tell if the angle is <90° if it is oriented upside down or if one of the rays is not aligned horizontally.
• Show how to put the square corner of a piece of paper into the angle to check. If the paper covers up the angle, it is <90°.
2. Students are told an acute angle “is a cute little angle.”  I am guilty of having done this in the past. But if a student sees any angle made up of short lines, they may interpret it as “little” or acute.
• Remind them it’s the size of the angle that makes it acute, not the size of the lines.
3. While right angles are exactly 90°, students may expect an acute angle to be given a specific number.
• Acute angles range from 1° to 89°. Obtuse Angles (angles greater than 90°): Continue reading