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### Course: Geometry (all content)>Unit 2

Lesson 8: Sal's old angle videos

# Angles (part 2)

More on complementary and supplementary angles. Introduction to opposite angles. Created by Sal Khan.

## Want to join the conversation?

• Can someone explain what an "adjacent" angle is?
• Adjacent angles are two angles in a plane that have the same vertex and a common side (of the angles) but no common points except for points on the common side and the vertex
• isn't a 360 degree a cricle i'm confused and whats the difference between supplementary and complemtary at
• A supplementary is a pair of angles with 180 degrees total while complementary is a pair of angles that equal 90degrees.
• I'm confused about 360° and 0°. Are they the same, is one a circle and one a straight line?
• Degrees are used to describe measures of angles, so it wouldn't exactly be either a "circle" or a "straight line", but instead it would be used to describe the measurement of the angle.

If you're trying to describe the measurement of the angle between two intersecting rays that intersect at a certain point, that, let's say have an angle of 30 degrees, it would NOT be incorrect to also say that they have an angle of 330 degrees (360 - 30 = 330), so therefore, when describing angles in this way, we could express "0 degrees" as "360 degrees" and also as "720 degrees", etc., and these would still describe the same two intersections.

If however, we were to describe the orbit of the Earth and compare this with Jupiter's orbit, and describe these orbits' angles in terms of degrees, we would not really be using lines, but what are known as "arcs" (plural for "arc"), which are basically lines cut from a circle, that in our case, represent the orbits of the planets. In this case, if we were to say that Earth orbited a total of 410 degrees for every 360 degrees of Jupiter's orbit, it would NOT be synonymous to also say 770 (= 410 + 360) degrees for every 360 degrees.

So for angles between lines, it doesn't hurt to think of them as the same. I hope that answered your question. I might be wrong in certain areas, but that's the way that I've always thought of it.
• What is an adjacent angle?
• An adjacent angle is an angle with a common ray coming out of the vertex going between two other rays. They are also side by side. Hope I helped :)
• what does supplemetary mean? At I think he said it but i still don't get it. please tell me.
• Supplementary angles are 2 angles that add up to 180 degrees.
• I thought of a hint to remember "supplementary." Supplementary angles add together to make a straight line. Both begin with S
• I put complementary and supplimentary in alphabetical order--and 90 comes before 180 so complimentary goes with 90 and supplimentary goes with the number 180.
(1 vote)
• what is a reflex angle, i have a big test tommorow on angles please help thanks ;)
• Your test probably passed....... Hope you passed. Well, a reflex angle is a angle which is more than 180 degrees however, less than a full circle, which is 360 degrees....... I'll vote up.
• adjacent angle is a a corner that is next