# Measuring angles with a circularÂ protractor

CCSS Math: 4.MD.C.6
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## Video transcript

- [Voiceover] Measure the angle in degrees. So here we have this blue angle that we want to measure in degrees, and it's sitting on top of this circle. That circle is actually a protractor. Sometimes we see, and maybe what you're used to seeing, is protractors that are more semicircle shaped, something like this. And those semicircle protractors measure from zero to 180 degrees. Which is good, but a circle is even better. A full circle is better because an angle can measure up to 360 degrees. So a full circle allows us to measure and angle of any size, instead of only an angle up to 180 degrees. Now the way we're gonna measure this angle is the same way we would on a semicircle protractor. The first thing we wanna do is make sure one of our rays lines up to zero. So here's one of our rays, and it's lining up to zero on the protractor. So that's nice, it's already lined up for us. And then we're gonna measure the opening all the way to the other ray, to right here. And so if our angle only measured opened up this far, it would be a 10 degree angle. If let's say it opened to here, it would be a 50 degree angle. But our angle measures all the way to here, to the 160 degrees. So 160 degrees is the measure of our angle. And again, when you measure on a circle protractor, or any protractor for that matter, you're gonna line one ray up to the zero, and then measure the opening 'til you get to the other ray, which in this case opened up to 160 degrees.