![]() Three years later, someone named Chad asked another question that was added on to this page: How do you use a protractor to find the three angle measures of a triangle?Īgain, the goal is a specific task, but this time it’s not finding and drawing an angle, but measuring one that is already there, as in my extra comment above. ![]() Have fun drawing and measuring, and let us know if you need more help, or if you discover any great theorems while you explore! Measuring angles in a triangle Then you read the numbers just like a ruler. Then you find which set of numbers starts at zero on the first line, and follow it until you come to the second line. You line up the bottom edge with one of the lines that make the angle, with the center mark (C) over the place where the lines meet. Though the question was only about drawing an angle, I added a comment on the opposite task: If you have to measure an angle you've been given - maybe where the line you just drew meets the other parallel line - then you do the same thing in reverse. There are 10 marks between 60 and 70, and we chose the large one in the middle, for 5. On my protractor, we used the inside numbers. Now you can use your ruler to draw a line between the marks (CD), and you're done! Make a small mark there (D), and then remove the protractor. Just as on a ruler, there should be some number of divisions between them, and you should be able to identify a mark for 65 degrees halfway between 60 and 70. To draw a line at a 65-degree angle, facing to the right, look for the numbers that start at 0 on the right (that's the outside set of numbers on mine) and look along them until you come to 60 and 70. Note that the vertex of the triangle does not go on the edge of the protractor (though that might be true for some that are not transparent like mine) the protractor has to be placed over the line you are using, with the vertex directly under the cross, and the line passing under the 0 mark. degree labels around the outside, probably going in bothĭirections (clockwise and counterclockwise) from 0 to 180. a semicircle around the edge, with little degree marks (so you should first make a small mark there to show Marks the center of the angle you are going to measure a cross or dot in the middle of that line (C), which With the line you want to make a 65 degree angle with a line along the bottom (AB), which you have to line up What you should see on yours (and on mine if I could draw it better!) are: Here is a better picture (of a really cheap school protractor!): Math, and inserting pictures was not easy, so I did it the hard way. Mine is not very round after passing through e-mail, but you should more or less recognize it: Let's take out your protractor and look closely at it. Michelle had a specific task to perform, but her main need was to learn how to use the protractor so I used the former as an example for the latter: Hi, Michelle. I made two parallel lines - now I have to intersect those lines making a 65-degree angle. I need to know how to find angles and to use a protractor. Math archive already, our first extended discussion of reading a basic protractor was this, in 1998: Using a Protractor Drawing or measuring an angleĪlthough there were several short answers in the Ask Dr. And just like last time, I’ll add a bonus: why it has that name. We’ll also consider the relationship between protractors and the compass and straightedge constructions that started this series on geometry tools. ![]() This time, we’ll consider another common question over the years: how to use a protractor to measure angles. ![]() Last time we looked at how to use a ruler to measure distances.
0 Comments
Leave a Reply. |