## The Lesson

Degrees are a unit of measurement of an angle. There are 360 degrees in a full rotation.

## Dictionary Definition

The Oxford English Dictionary defines a degree as "a unit of measurement of angles or circular arcs, being an angle equal to the 90th part of a right angle, or an arc equal to the 360th part of the circumference of a circle (which subtends this angle at the centre)."

## A Real Example of Degrees

An angle measured in degrees is written as number followed by the degree symbol °:

This is 90° (said as "90 degrees").

## 360 Degrees in a Circle

There are 360 degrees in a full rotation (a circle). One degree is 1360th of a circle.

## How to Measure an Angle in Degrees

The number of degrees in an angle can be measured directly using a protractor:

Alternatively, geometry and trigonometry can be used to find angles.

## Important Angles in Degrees

• 90° is a right angle, a quarter of a rotation.

• 180° is a straight angle, a half of a rotation.

• 270° is three quarters of a rotation.

• 360° is a full angle, a whole rotation.