Know the Types of Angles

Types of angles – In math lessons someone must explain angles. Lessons or material about angles will usually appear at every level of education. This is because angles are always present in everyday life. In fact, the houses we live in are built using good and correct angles, so they look beautiful and sturdy.

However, for some people they only know what an angle is and don’t know the types of angles and how to measure angles. Sinaumed’s, the article will discuss the meaning of angles, types of angles, and how to measure angles. So, read this article until it’s finished.


Definition of Angle

Any building that has not yet been built will definitely be drafted first. If you pay attention to the design of this building, it is an interconnected line, thus forming a single unit. The interconnected lines will form an angle that can strengthen the building and beautify the building.

Apart from building, angles can also be found in the world of sports, one of which is soccer. In football there is such a thing as a “corner kick”. Why is it called a “corner kick”? Because the ball to be kicked is in the corner of the field or the meeting point between the horizontal and vertical lines.

Apart from “corner kicks”, corners in soccer can be found at the goal or more precisely at the top right and top left of the goal.

Therefore, in everyday life almost every object that we see must have an angle. However, do you know what an angle is? An angle is a shape resulting from two lines meeting each other. Meanwhile, an angle can be said to be a space between two straight lines that intersect each other if they are in a two-dimensional shape with regular sizes.

Meanwhile, in the Big Indonesian Dictionary, an angle is a shape made by two intersecting lines around the point of intersection. Therefore, in simple terms, an angle is a shape formed by the existence of two intersecting straight lines that meet at the same point.


Coat, Emblem Name, and Angle Name

Sinaumed’s, do you know the shape and name of the angle symbol? Angles have a symbol like this “?”. While the angle symbol is usually referred to as “alpha” or “theta”. The angle symbol will usually be placed before giving the angle name. You can see an example of an angle below.

From this angular example, the correct angular names are ?ABC and ?CBA, why is that? Because the letter “B” is the meeting point of the CB and AB lines. While writing the wrong corner names such as ?ACB and ?CAB. The name of the angle is incorrect because the letters “A” and “B” are not intersection lines or lines that intersect.

How about Sinaumed’s, how to write angular names is very easy right? The thing that needs to be underlined in writing from angular names is not to misplace the letters. If you put the letters wrong, then the angle you read will be wrong too.


Types of Angles Based on the Big Angle 

The types of angles are divided into two parts, namely based on the size of the angle and based on its position. The types of angles based on the size of the angle consist of 7 types of angles, namely acute angle, right angle, angle, obtuse, straight angle, reflex angle, zero degree angle, and full angle.

1. Sharp angle

An acute angle is an angle that has an angle that is not more than 90 degrees or more precisely, the size of an acute angle is between 0 degrees and less than 90 degrees. The magnitude of the acute angle is practically smaller when compared to the right angle. If using mathematical symbols can be seen below

0 degrees < x < 90 degrees (x is the measured angle)

The acute angle has another name in English in the form of an acute angle . Any triangle that has an angle less than 90 degrees has an acute angle. Acute angles are usually found in triangles, parallelogram trapezoids, etc.

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You can find sharp angles in everyday life, such as slices of pizza, a clock that shows 11 o’clock, clothespins, the tip of an iron, and the letter A.

2. Right angle

A right angle is an angle that has a very precise angle of 90 degrees. This right angle results from two straight lines that intersect or meet, thus producing lines that are perpendicular to each other. A right angle can be said to be larger than an acute angle and smaller than an obtuse angle.

Right angles in English are usually known as tight angles . If a triangle has angles of exactly 90 degrees, then the triangle is called a right triangle.

Meanwhile, we can find right angles in everyday life, such as all the walls of houses, cupboards, clocks that strike three o’clock, photo frames, windows, books, and ceramics.

3. Obtuse angle

An obtuse angle is an angle that has an angle of more than 90 degrees or more precisely above 90 degrees and below 180 degrees. An obtuse angle can be said to be an angle whose measure is above a right angle and an acute angle. If using mathematical symbols can be seen below.

90 degrees < x < 180 degrees (x is the measured angle).

An obtuse angle in English is usually known as an obtuse angle . A triangle whose one of the angles has angles greater than 90 degrees, then the triangle is called an obtuse triangle. Triangles that have obtuse angles are isosceles triangles and areosceles triangles.

Obtuse angles can be found in everyday life, such as boomerangs, clocks that strike 7 o’clock, rooftops, beach chairs, rocking chairs, and hockey sticks.

4. Straight angle

A straight angle is an angle that has a measure of 180 degrees. At a glance, a straight angle is like a straight line with a horizontal shape and looks like it has two arms.

Although straight angles are like straight lines, they are very different from angles with 0 degrees. A straight angle in English has another name, namely a straight angle .

In everyday life, you can find straight angles, such as walls, table bases, clocks that show 6 o’clock.

5. Reflex angle

A reflex angle is an angle that has an angle ranging from 180 degrees to less than 360 degrees. With the size of the angle that is owned by the reflex angle, it can be said that the magnitude of this angle is greater than obtuse angles, right angles, and acute angles. It is called a reflex angle because this angle is a reflection of an obtuse angle. If using mathematical symbols can be seen below.

180 degrees < x < 360 degrees (x is the angle to be measured)

The reflex angle in English is called the reflex angle . The size of the angle that is owned by the reflex angle, this angle has more than one straight angle, but does not reach full rotation.

6. Zero degree angle

A zero degree angle is an angle whose angle measure is only zero degrees. A zero degree angle is an angle formed by two lines that coincide with each other, but do not form an angular area. At first glance it looks like two straight lines, but in fact the two lines are coincident. Therefore, this angle is very difficult to imagine the shape.

In English, the zero degree angle is commonly referred to as zero degree . In everyday life it is very difficult to find a zero degree angle because almost every item that exists must have an angle.

7. Full angle

A complete angle is an angle that has an angle of 360 degrees. Therefore, full angles usually have a tendency to form a circle. A straight line that is at full angle will usually fulfill one rotation which results in a 360 degree angle or succeeding to its initial position requires a rotation.

In English, this full angle is often referred to as the complete angle. It can be called the complete angle because this angle can fulfill one full rotation. In addition, a full angle can be said to be an angle that can rotate in the opposite direction to the other line until it reaches the other line.


Types of Angles Based on Position

The types of angles based on the position consist of four types of angles, namely adjacent angles, vertical angles, complementary angles, and supplementary angles.

1. Adjacent angles

The picture above explains that adjacent angles have three lines. Therefore, adjacent angles are the angles resulting from three lines connected by a single vertex. A vertex point is a point that meets three or more lines at an angle.

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2. Vertical Angle

The picture above explains that the vertical angle has two angles. So, a vertical angle is an angle that results from two opposite angles meeting each other, thus forming an intersection of two lines. Therefore, the vertical angle can also be called the opposite angle.

3. Complementary Angles

The picture above explains that in the middle of a right angle there is a line that forms two angles. Complementary angles are angles formed by meeting two adjacent angles with an angle measure of exactly 90 degrees.

4. Supplementary Angle

The picture above explains that in the middle of a straight angle there is a line that creates two angles. A supplementary angle is an angle formed by the meeting of two adjacent angles with a measure of exactly 180 degrees.


How to Measure Angles

Sinaumed’s, do you know the name of the tool for measuring angles? Yes, that’s right, the name of the tool for measuring angles is a protractor. Therefore, the arc is often dubbed as a protractor (a unit commonly used for angles). So how do you use a protractor? Take it easy, below we will explain more about how to measure angles with a protractor.

1. Put the bow at point A

2. Adjust well until the base line of the bow is in the right position (coincides) on one corner of the corner leg. For example line AB.

3. Then measure the angle starting from 0 degrees which is located on the AB line until it reaches the CA angle.

4. The picture above shows that the CA line is at 60 degrees (using the internal scale).

5. So, the angle measured is 60 degrees, so it can be said that the angle above is included in the acute angle.

How to measure angles with a protractor, very easy right? Sinaumed’s, you can practice how to measure at school or at home.

How to Draw Angles

It feels incomplete if you only discuss how to measure angles, but don’t discuss how to draw angles. Below will explain how to draw angles.

1. First make a horizontal line AB

2. Then place the center of the arc at point A or at 0 degrees.

3. Decide what angle to draw.

4. Determine the size of the angle according to the angle you want to draw.

5. After determining the angle, then put a mark at point C.

6. If so, it will form the desired angle. Like the example of the angle above.

Angles and their Relationships

For some people, they may only know that the unit for angles is only degrees, but actually there are four angle units, namely degrees, radians, the sexagesimal system, and the centesimal system.

1. Degrees

The degree unit of angle commonly used to form a flat plane shape. The units of degrees are divided into 360 degrees or it can be said that one full rotation has 360 degrees. Therefore, an arc that shows one degree is a sign that one sector of the circle is divided into 360 wedges of the same magnitude.

2. Radians

Radian is a unit of angle in a plane. The symbol for a radian is “rad” and 1 radian or 1 rad is a central angle that has an arc length equal to the radius of the circle. 1 radian or 1 rad equals 57.2960 which, when rounded, becomes 57.30. Meanwhile, one degree equals phi divided by 180

3. Sexagesimal System

The sexagesimal system is a number system based on 60. This number system has existed since 2000 BC and originates from the Sumerians. Until now, the sexagesimal number system is still used to measure various things, such as angles, time, and geographic coordinates. In this system, there are two angular units, namely minutes (‘) and seconds (“”).

If read 1 degree is equal to 60 minutes. Therefore, if you want to convert degrees to minutes, just multiply it by 60. If you want to convert minutes to degrees, just divide by 60. If formulated, like

4. Centesimal System

In the centesimal system, the units used are called grads . 1 right angle is equal to 100 grad.


Angle is one of the important math lessons to learn, especially for those of you who want to aspire to be an architect. Angles that we often know are usually types of angles based on the size of the angle, because we can see it in everyday life. Angle units consist of four kinds, namely degrees, radians, sexagesima system, and centesimal system. However, the unit of angle that is often used by most people is the degree.