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Measuring Angles

To measure angles precisely, mathematicians divided the circle into 360 equal parts. Each part
represents 1 degree, written as 1°. The idea is that the measure of an angle is simply the number of
these 1° units that fit inside it.
For example:
 An angle that contains 30 of these units would have a measure of 30°.

Measures of Different Angles

 Full Turn: A full circle contains 360°. So, a full turn is 360°.

 Straight Angle: A straight angle is half of a full turn. Since a full turn is 360°, a straight angle
is 180°.
 Right Angle: Two right angles together make a straight angle. Since a straight angle is 180°, a
right angle is 90°.

For example, if you look at the hands of a clock, the angle between them at different times can be
measured in degrees. At 3 o'clock, the angle between the hour and minute hands is a right angle
(90°).

Why 360 Degrees?
But why 360°? The exact reason is a bit of a mystery, but there are several historical reasons:

 Ancient civilizations, like those in India, Persia, Babylon, and Egypt, used a year with 360 days
in their calendars.

 The number 360 is practical because it can be divided evenly by many numbers (like 1, 2, 3,
4, 5, 6, 8, 9, 10, and 12), making it easier to split a circle into equal parts.

This divisibility is why 360° has been used for so long—it’s just really convenient!

Degree Measures of Angles