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### Course: Integrated math 2>Unit 11

Lesson 2: Arc measure

# Finding arc measures

Watch Sal solve a few problems where he finds a missing arc measure.

## Want to join the conversation?

• At , isn't the major arc also Arc AC, so wouldn't that be really confusing that both the minor arc and the major arc are called the same thing? Shouldn't the minor arc be called Arc ABC in this case?
• Hi Hisham Malik,

The major arc has to be denoted with three letters so it will be called arc ACB. The minor arc is always two letters so in this case it is AC. Always remember that a major arc is always 180˙ or more.

Hope that helps!
- JK
• Wait, so Sal means that the angle value is the same as the arc measure? I thought they were two different things. My math teacher said so. Please help.
• The arc measure is equal to the angle value. It's just like taking a protractor to those two lines. However, the arc LENGTH is different. The arc length would be like cutting that piece of the circle off and measuring it with a ruler, therefore it is measured in inches, mm, etc.
• What if an arc is exactly 180 degrees? Is it a major or minor arc? (Sorry if this is a stupid question :P)
• An arc that is exactly 180 degrees is a semicircle. Also, that's actually a really good question.
• i think the first example was poorly phrased, wouldn't the correct answer be 186 degrees because you're looking for arc AC instead of ABC? typically, the major arc contains three points on the circle but in this scenario the minor arc does, so how do you determine which arc you're looking for? asking for a friend
• Not at all. The minor arc only needs the two endpoints to identify it, there could be as many points in between these as you want (in this case only one), it does not change the name of it. Major arcs must have three letters to distinguish them from minor arcs, so there would have to be another point D on the opposite side of the circle from B to distinguish it as major arc ADC.
• For the second example, the question says that both AD and CE are diameters of circle P, and I was a bit confused because if both of them are diameters, wouldn't that split the circle into fourths that all equal 90 degrees? How would angle EPD equal 93 degrees when the circle is cut by two diameters? Am I missing something?
• Two diameters need not be perpendicular. Being a diameter just means it passes through the center of the circle. It can be rotated any angle.
• Anyone else think Sal's voice sounds hoarse in this video?
• Not really.
• Is being a minor arc a bad thing or a good thing?
• It actually basically doesn't basically technically essentially matter at all. So there you go! :-)
• I thought that it would be major since it takes three angles. So how is it the minor?
(1 vote)
• For the first question if arc AC is the minor arc, then what would be the major arc?