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## Class 9 (Assamese)

### Course: Class 9 (Assamese)>Unit 6

Lesson 1: Pairs of angles

# Complementary & supplementary angles

Learn about complementary and supplementary angles, as well as the definitions of adjacent and straight angles. Created by Sal Khan.

## Want to join the conversation?

• Do complementary and supplementary angles have to be adjacent?
• They don't have to be adjacent but if they are they form a straight line on the sides that they don't share.
• Does anyone have any hacks for remembering this I have a test on Friday
• Try this:
Complementary angles add up to 90°
- example: 15° & 75° are complementary
(added together, they form a right angle)
-and-
Supplementary angles add up to 180°
- example: 50° & 130° are supplementary
(added together, they form a straight line)

Two facts:
(1) 90° comes before 180° on the number line
(2) "C" comes before "S" in the alphabet

90° goes with "C" for complementary
so complementary angles add up to 90°

180° goes with "S" for supplementary
so supplementary angles add up to 180°

Hope this helps!
• Definition of linear pair?
• Two angles are linear if they are adjacent angles formed by two intersecting lines. A straight angle is 180 degrees so 2 linear pairs of angles must always add up to 180 degrees.

Hope that this is helpful to u
• can you tell me a trick for remembering suplementory and complimentory angles.
• The easiest way to remember the difference between supplementary and complementary angles is to use the starting letters of the words themselves. Think of the "C" as a corner, which reminds you of a right angle, which is 90 degrees. Think of the "S" as straight, which reminds you of a straight angle, which is 180 degrees.

Hope this helps :)
• So how do you know if its complementary
• If two angles add up to 90 degrees then they are complementary, if they add up to 180 degrees they they are supplementary
• Do we have names for angles that add up to 270 and 360 degrees?
• There are currently no name for 2 angles that add up to 270 degrees but Explementary Angles are the name for a pair of angles that adds up to 360 degrees, even if an angle is more than 180 degrees

• Is there a video about the angle pairs, specifically? Because I don't remember seeing anything about it.
• I think this is the only one. A pair is a group of two. So a pair of angles = two angles.
• How do I determine if it's complementary or supplementary?
• complementary angles add up to 90 degrees. a supplementary angle adds up to 180 degrees.