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Degrees
Definition: A measure of an angle. One degree is one 360th part of a full circle.
Try this
Adjust the angle below by dragging the orange dots at Q and R. Note the number of degrees for any particular angle.
(If there is no image below, see support page.)
Measure of an angle
In geometry an angle is measured in degrees, where a full circle is 360 degrees. As in the figure above, a smallish angle might be around 30 degrees.
The degree is further divided in to 60 minutes. For even finer measurements the minute is divided again into 60 seconds,
However this last measure is so small, it only used where angles are subtended over extreme distances such as astronomical measurements, and measuring latitude and longitude.
Terminology
| Unit |
Written |
Pronounced |
| Degrees |
With a small circle after the number.
Example 61° |
"61 degrees" |
| Minutes |
With a small dash after the number.
Example 34° 21' |
"34 degrees, 21 minutes" |
| Seconds |
With two small dashes.
Example 32° 34' 44'' |
"32 degrees, 34 minutes, 44 seconds" |
When minutes and seconds are used alone, we usually say "arc minutes" and "arc seconds" to avoid confusion with time units.
What you should know
Use the figure above to become familiar with what various angle measures look like when measured in degrees. In general, you should be able
to visually estimate any angle to within about 15°, and you should be able to recognize the common angles (shown in red) on sight and sketch them yourself.
Other measures - radians, grads
An angle can be measured in radians where the full circle is 2 pi radians (about 6.28).
This is used extensively in trigonometry.
In some surveying work the grad is used. There are 400 grads in a circle and so a right angle is 100 grads. You will rarely see this unit. Think of grads as 'metric degrees'.
Related angle topics
General
Angle Types
Angle relationships
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