What is a protractor? A tool that is used to measure angles and may be found in a geometry set is called a protractor. Protractors are often constructed of plastic. The protractor may also be used to draw angles with specific measurements, expressed in degrees. One example of the many kinds of protractors available is the circle protractor, which can measure angles of up to 360 degrees. In this article, let’s dive deep into the protractor as well as how to use it!
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What is a Protractor?
In geometry, a protractor has the form of a half-circle and is often split into 180 equal pieces; each of these parts represents one degree of angle. As a result, the standard protractor included in a geometry box is capable of measuring angles up to 180 degrees.
Most of the protractors that we have in our geometry box are made of plastic, but some of them are also constructed of wood, steel, and even glass in certain instances. Radian-scale protractors are rare protractors that can measure angles in radians. Degree-scale protractors are the most common kind of protractor. Radian-scale protractors measure angles in radians.
Protractor is widely used in mechanical engineering but is especially frequently used in schools. Protractors are usually flat, but some elaborate types have two extra swivel arms for more accurate angle measurements.
History of the Protractor
The protractor precursor was found in the tomb of an Egyptian architect, circa 1400 BC. The first protractor was made more than five hundred years ago. A book, written by writer Thomas Blundeville described an instrument specifically designed to measure angles.
The author of that book used a protractor to prepare maps and navigational charts for high-latitude use. Several other European mathematicians also wrote about the protractor at the same time, so it is not known who invented it first.
In the eighteenth century, the protractor was widely used in geometry and mathematics, by the nineteenth century, many different versions of the protractor appeared.
Structure of Protractor
Depending on the type of protractor, there are different types of ruler construction, but most of them have one thing in common: a half circle is divided into 180 equal parts, recorded from 0 degrees to 180 degrees, The center of the semicircle is the center of the ruler, which is considered a 180-degree protractor.
- Angles are measured in degrees, the representation of degrees is a small circle
- The great circle is 360 degrees, and its half circle or straight angle is 180 degrees.
- A half circle or part of its right angle is 90 degrees.
Properties of Protractor
The most basic form of a protractor is a piece of material in the shape of a half circle with degree marks scratched into the outer edge of the arc, also known as a curved section. After positioning the straight edge along one of the lines to be measured, the location at where the arc is intersected by the second line is used to calculate the total number of degrees.
The standard protractor can only measure angles up to 180 degrees since it is shaped like a half circle. This is sufficient for the typical use since the connection between two lines can always be stated as an angle that is less than or equal to 180 degrees. Simply turning the protractor over will give you a reading that is less than 180 degrees if the way it was first positioned caused it to create an angle that was more than 180 degrees.
This is because the circle is symmetrical; beginning at one line, the angle to a second crossing line may be determined by going either clockwise or counterclockwise around the circle. This is because the circle has no straight edges.
When measured in one way, the angle will be larger than 180 degrees, whereas when measured in the other direction, the angle will be less than 180 degrees. They must total up to 360, which is the number of degrees in a complete circle, hence none of them may measure more than 180 degrees individually.
How to Use a Protractor?
Measure an Angle with a Protractor
Allow us to walk you through the process of measuring an angle using a protractor, step by step.
- Step 1: First, let’s assume there is an angle denoted by AOB, the length of which has to be determined. The zero point of the protractor should be exactly positioned on the vertex of the specified angle, and the base arm of the angle should coincide with the line that represents 0 degrees on the protractor.
- Step 2: When we have finished precisely positioning the protractor, we read the measure of the angle. Because we are measuring in the counterclockwise direction, we read the inner calibration.
- Step 3: At this point, pay close attention and make a note of the marking.
Draw an Angle with a Protractor
Let us go through the process of drawing an angle with a protractor, step by step.
- Step 1: In the first step, use a ruler to draw the line segment AB.
- Step 2: Next, position the protractor on one of the ends of the line segment AB in such a way that the zero of the protractor corresponds with the end of the line segment, and the base of the protractor coincides with the line segment. Create a mark at the spot where you wish to make the increased degree angle.
- Step 3: Involves taking away the protractor and using a ruler and a pencil to connect the indicated point to point A of the line segment.
Important Notes When Using the Protractor
Obviously, this will be the type of ruler that is no stranger to every student. A protractor is an indispensable tool with the function to assist you in determining measurements for geometry problems. It is also a great tool to help you solve as well as process the given data in a convenient and fast way.
- Check the zero point before measuring because determining the accuracy when measuring a lot. If the 0 point is skewed, even an accurate measurement will not give an accurate result.
- Place the edge of the ruler so that the body of the ruler coincides with the edge to be measured and the center of the ruler coincides with the top of the angle to be measured. Avoid deviating the length of the line from the ruler because that will lead to quite a bit of error.
- It is necessary to clean the ruler regularly to avoid the parameters and measurements being worn or covered with dust, making it difficult to read the results.
- You need to pay close attention to the parameters and units of measurement before paying for a protractor.
- You should consult experienced people to ask how much to buy a protractor to avoid buying too expensive compared to the market price.
Read more >> What are Vertices? What are Edges? Definition, Examples of Vertices & Edges
Preserve the Protractor
To ensure increased product life, and stable and error-free operation, users need to adhere to the following principles:
- Do not place and use the ruler on rough, dirty surfaces as this may interfere with determining the angle measure.
- Special care should be taken while removing the ruler from the measuring object and reading the measured value because it is easy to cause errors in the calculation process.
- Be sure to clean the ruler before measuring. Besides, the ruler after use should be cleaned to avoid the characters on the ruler being blurred.
Final Words
What is a protractor? The answer has been detailedly mentioned above. Hope that this article on protractors can give you the most beneficial information to solve math problems. If you are planning to teach your kids about this essential topic, you can make your own collections of protractor worksheets using our worksheet maker. Good luck!
