What is a Protractor?
” Can you help RG and Hannie solve some problems using a protractor? • To help complete the scenario, ask students to define a protractor. Explain that a protractor is a tool used to measure angles. Ask the students if they have seen or used a protractor before. • Next, pair students together and provide each group with a protractor. Instruct students to make a list of observations based on the physical appearance of the protractor. Create a class list of observations by allowing each group to share 1 or 2 observations. The list may include the following: • It is shaped like a semi circle (although some protractors can be a full circle) • It looks like a ruler • It has numbers labeled from 0 to 180 • There are two rows or scales of numbers • The upper scale starts with 0 on the left side and increases to 180 on the right • The lower scale starts with 180 on the left side and decreases to 0 on the right • The upper scale measures angles with openings on the left • The lower scale measur
A protractor is a device for measuring the angle between two intersecting lines. The angle is measured in degrees, and a circle is defined as having 360 degrees of identical size. The earliest known protractors were designed in the 17th century by sailors needing to plot courses on nautical charts. A basic protractor consists of a half-circular piece of material with degree markings notched onto the outside edge of the arc, or curved section. The straight edge is placed along one of the lines to be measured, and the number of degrees is determined by where the second line crosses the arc. Because it is a half-circle, the basic protractor only measures angles up to 180 degrees. This is adequate in normal use, as the relationship between two lines can always be expressed as an angle of 180 degrees or less. If the original placement of the protractor produces an angle greater than 180 degrees, simply flipping it over will provide a reading of less than 180 degrees. This is due to the symm
A protractor is a clear plastic device to measure angles from 0 to 180 degrees. You can use a protractor to measure an angle in degrees. How do I measure angles using a protractor? There are two sets of numbers, so you can measure angles from either side of the protractor. To decide which scale to use, look at the angle you’re measuring. If it is greater than a right angle (more than ninety degrees) then use the scale that has numbers greater than 90. If the angle is acute (measures less than 90 degrees), use the scale which has numbers less than 90. Example: right angle A right angle measures 90 degrees. Measure an angle by measuring the distance between its sides. Place the protractor on the angle so that the center point is on the vertex and the zero line is along one side of the angle. Follow the scale beginning at zero and read the measure of the angle where the other side of the angle intersects the scale on the protractor. Example: acute angle An acute angle is less than 90 degr
