![using a protractor using a protractor](https://i.ytimg.com/vi/EdYyx2h0LwY/maxresdefault.jpg)
Mark the paper where the vertex is placed. STEP 2 Place the origin of the protractor at one end of the line. You can use the flat edge of your protractor to draw this line.
![using a protractor using a protractor](https://ecdn.teacherspayteachers.com/thumbitem/Protractor-Guide-Measuring-Angles-2599730-1495978979/original-2599730-1.jpg)
It’s generally easiest to draw the straight line in a horizontal position on the paper. It will be used to determine the position at which you draw the second arm of the angle. The line is your reference line and the first arm of your angle. Use scale with zero mark lying on the arm of the angle. NB: When measuring a reflex angle, subtract the value of the acute angle from 360. If the angle was obtuse, we would use the scale that indicated an angle larger than 90 degrees. We use the smaller scale because we determined that our angle was less than 90 degrees in the first step. In the above example, the angle measure is 30 degrees. The number the line passes through is the angle’s measurement in degrees. Alternatively, you can align the edge of a piece of paper with the angle’s arm to pass beyond the edge of the protractor, continuing the line of the angle. If the line does not pass through the protractor’s arc, extend the angle’s line until it does. STEP 4 Follow the opposite arm of the angle up to the measurements on the protractor’s arc. It is aligned with the center of the origin and the line projects to the start of the scale on either side. NB The baseline is parallel to the edge, but is not the flat edge of the protractor. Maintain the vertex of the angle in the origin and gently rotate the protractor so that one of the arms of the angle falls on the baseline of the protractor. STEP 3 Rotate the protractor to align one arm of the angle with the baseline. Align the vertex of the angle with the center of the cross in the origin The small hole in the middle of the base of the protractor is the origin. STEP 2 Place the origin over the center point, or vertex, of the angle you want to measure. At a glance, we can tell this angle is acute because it is less than 90 degrees. Doing this first step helps you identify which scale to use on the protractor. Right angles are exactly 90 degrees (two lines perpendicular to each other). You can easily identify by eye, the category of angle you are trying to measure. Obtuse angles are wide (greater than 90 degrees). Īngles can be classified in three ways: acute, obtuse, and right.Īcute angles are narrow (less than 90 degrees). STEP 1 Approximate the measure of your angle. By understanding how the parts of a protractor are used together and following a few easy steps, you will be an angle expert in no time.
#USING A PROTRACTOR HOW TO#
How to Use a Protractor to Measure Angles
![using a protractor using a protractor](https://image1.slideserve.com/2577703/determine-azimuth-on-a-map-using-a-military-protractor-l.jpg)
A semi-circular protractor displays a straight angle Generally, semi-circular in shape, protractors are also available in full-circle, 360-degree versions. This makes the tool handy for measuring angles originating from either direction. Most protractors have two opposing ruler grids, one on the inner side of the arc and one on the outer. The measurement scale may seem confusing. At the end of the lesson, the students should be able to use a protractor to measure and draw angles.Ī protractor is a handy tool used to measure and draw angles.