A protractor is a mathematical instrument made from clear plastic used for measuring angles in degrees such as the angles of a triangle or a hexagon.
Types of Protractor
Semi-Circular Protractor: This protractor has two sets of scales graduated up to 180° in opposite directions enabling angles to be read from two directions. On the base of the protractor is a midpoint mark that indicates the position of the highest point of the angle that is going to be measured or the vertex. The semi-circular protractor is used for reading, drawing and plotting angles on paper or charts. This type of protractor is commonly used in classrooms for geometry and in mechanical and engineering-related applications.
The Vernier Scale: This is used on protractors to enable them to give more precise and accurate measurements. There are 60 minutes in a degree and regular protractors have a scale graduated in degrees. In the Vernier scale, each graduation represents 5 minutes or 1/12 of a degree. The Vernier scale is found underneath the main degree scale and is spaced so it reads at a constant fraction of the fixed main scale.