Protractor

A protractor is a measuring instrument, typically made of transparent plastic or glass, for measuring angles. Most protractors measure angles in degrees (°). Radian-scale protractors measure angles in radians. Some protractors are simple half-discs; these have existed since ancient times. More advanced protractors, such as the Bevel protractor, have one or two swinging arms, which can be used to help measure the angle.

History

The protractor has been used since ancient times. The earliest recorded use of a protractor dates back to the ancient Egyptians, who used a simple form of the instrument for architectural purposes. The modern protractor, as we know it, was developed in the 16th century.

Types of Protractors

There are several types of protractors, each designed for specific applications:

• Simple Protractor: A basic semicircular tool used to measure angles up to 180°.
• Full-Circle Protractor: A circular protractor that can measure angles up to 360°.
• Bevel Protractor: A more complex instrument with a pivoted arm, used for precise angle measurements.
• Digital Protractor: An electronic version that provides a digital readout of the angle.

Uses

Protractors are used in various fields, including:

• Geometry: To measure and draw angles.
• Engineering: For precise angle measurements in design and construction.
• Navigation: Mariners use protractors to chart courses.
• Art: Artists use protractors to create accurate angles in their work.

How to Use a Protractor

To measure an angle using a protractor:

1. Place the midpoint of the protractor on the vertex of the angle. 2. Align one side of the angle with the zero line of the protractor. 3. Read the number on the protractor where the other side of the angle intersects the number scale.

Related Pages

• Angle
• Geometry
• Bevel protractor
• Radian
• Degree (angle)
• Navigation