Online protractor v0.1.0
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A protractor to drag and turn on the board. Line it up with an angle and read the scale, then show the answer to check.
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How to use it
- Drag the black corner dot so it sits at the angle's corner, or leave it where it is.
- Turn the protractor with the dot on its right so its flat edge lies along one red ray.
- Read the number where the other ray crosses the scale that starts at 0 on your ray.
- Tick “Show the angle” to check, or press New angle for another one.
Ideas for class
- Estimate first: is it acute, right or obtuse? Then measure.
- Make a right angle and a straight angle and talk about how many degrees each is.
- Ask why two numbers are printed at each mark, and which one to use.
- Make an angle more than 90, show it with the protractor flipped, and see that the same ray reads two ways.
- Add two angles that share a ray and check that the sum is the big angle.
Related
Questions
Why are there two scales?
A protractor is read from either end. Use the scale that starts at 0 on the ray you lined up.
How exact is the readout?
To the nearest degree.
Can students use it on a tablet?
Yes. The dots are big enough to drag with a finger.
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