# Measurement of Angles

An **angle** is the region of the plane between two rays with common origin. The rays are called **sides** and have a common origin, the **vertex**.

An angle is positive if rotated in a counterclockwise direction and negative when rotated clockwise.

Angles are measured using the following units:

1.**Sexagesimal degree (°)**

If the circumference of a circle is divided into 360 equal parts, the central angle corresponding to each of its 360 parts is an angle of one degree sexagesimal, (1°).

A **degree** has **60 minutes** (') and a **minute** has **60 seconds** ('').

2.** Radian (rad)**

It is the measure of an **angle** whose **arc is a radio**.

2 rad = 360°

rad = 180°

30º rad

/3 rad º

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