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Concept

Protractor

A protractor is a tool used for measuring and drawing angles angles at specific measures.
A protractor

The protractor consists of a rounded-half-circle and a straight edge. The rounded part is marked in degrees from to This measuring scale is used for determining angles. The straight line at the bottom helps correctly align the measures. Its central mark is the midpoint, and the full length of the line is the diameter of the half circle.

Highlighted parts of a typical protractor

To find an angle measure using a protractor follow these steps.

  1. Position the protractor at the vertex of the angle.
  2. Be sure that the mark in the middle of the straight line aligns with the vertex.
  3. Align one arm of the angle with the baseline
  4. Read the degrees where the second arm intersects the scale.
An angle measured using a protractor
A protractor also measures and sets angles in real life. Carpenters use it to measure angles when cutting wood for joints, ensuring pieces fit together. Architects often use it to create and check angles in building designs and blueprints.

Extra

 Creating an Angle with a Specified Measure

A protractor can also be used to create an angle with a specific measurement.

  1. Position the midpoint mark over the vertex of the angle.
  2. Align the line with the direction of one ray.
  3. Then, make two marks — one at and one at the desired angle measurement.
Angle marks

Lastly, remove the protractor and draw rays from the vertex through the marked points.

Angle with a specific measurement
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