# What are complementary and supplementary angles?

Welcome to MooMooMath
In this video I would like to talk about complementary and supplementary angles.
This symbol is the symbol for angles.
complementary angles are two angles that add to 90 degrees.
A angle of 30 degrees is the complement of what angle?
The definition says" I take 30 plus an unknown angle (x) and it will add to 90.
Subtract 30 from both sides and x =60
So that will be a 60 degree angle.
Now let's look at an application of complementary.
In a right triangle, two acute angles are complementary.
If I know one ngle is 68 I can subtract it from 90 and I get 22 degrees.
So this angle is 22.
So 68 and 22 are complements of each other.
Now let's look at supplementary angles.
A supplementary angle is two angles that add to 180.
It is similar to complementary, which is 90 and supplementary is 180.
So an angle of 105 is the supplement of what angle?
Take x plus our 105 angle measure and set it to 180.
Subtract 105 from both sides so x = 75 degrees.
So 105 and 75 are supplementary angles.
Let's look at an application problem of this concept.
This is a straight line.
A straight line has 180 degrees.
When you draw an angle you will have two angles that are supplementary.
If this angle is 65,
What is the unknown angle.
Supplementary,take 180 minus 65 and I'm left with,115.
So the angle measure will be 115 degrees.
Rules of supplementary and complementary
Complementary are two angles that equal 90 degrees
Supplementary are two angles that add to 180 degres.
60 plus 120 equals 180
60 and 120 are supplements.