Imagine two lines that are going to intersect at a point. The point at which they intersect will create an angle. The angle is the deviation of another line from a reference. Basically, an angle is the region of the plane between two rays with a common origin. The rays are called sides and have a common origin, the vertex.

In the above image, the a and b are sides but in some textbooks, they are denoted by arms as well so don't get confused in terminologies, they both are the same. The point O is the vertex and a vertex is a point where both lines or planes meet each other. An angle is positive if rotated in a counterclockwise direction and negative when rotated clockwise. There are different types of angles, let's take a look at them:

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Types of Angles

1. Right-Angle

If the two straight lines/rays/planes (one horizontal and one vertical) meet each other, they will create a right angle. The identification of the right angle is that it will always be equal to

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2. Acute Angle

If the angle created by the rays/planes/lines is less than

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, that means you are dealing with an acute angle.

3. Obtuse Angle

If the angle created by the rays/planes/lines is greater than

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, that means the angle is an obtuse angle.

4. Straight Angle

If two straight lines/planes/rays (both either horizontal or vertical) meet each other, they will create a straight angle. A straight angle will always make

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5. Complete Angle

A complete angle is formed when two planes/rays/lines overlap each other completely hence resulting in an angle of

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6. Reflex Angle

If the angle is more than

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but less than

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, that means you are dealing with a reflex angle. In addition, angles are measured in different units and each unit is very important to understand. Below are the types of units used to measure angles:

Types of Units For Measuring Angles

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, ( $\text{[math]}$ ).

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.

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Convert

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to radian.

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Cross multiply:

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Convert

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to degrees.

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Emma

I am passionate about travelling and currently live and work in Paris. I like to spend my time reading, gardening, running, learning languages and exploring new places.

Measurement of Angles