Angle Sum of a Triangle

• The sum of the measures of the interior angles of a triangle is 180^o.

• <1 + <2 + <3 = 180

Remember:
You can make multiple triangles of different sizes with one set of angles.
However, if you are given a set of side lengths, you are given the dimensions of a single triangle.

Notice the greater than symbol! It is NOT the greater than or equal to symbol.

Why do I need to know this?

• Sometimes you will NOT be given a picture and you have to determine if you can create a triangle given the number lengths provided.

• Example: Given the lengths 2, 5, and 8cm, can you create a triangle?

What if the sum equals the other side?

• Ex: 2, 5, 7 are given and if you add 2 + 5 you get 7.... 7 is not greater than 7, so you CANNOT create a triangle.

• 
  

Example of proving a triangle can be made with the given side lengths of 7, 8, and 9.

Example of proving a triangle cannot be made with the given side lengths of 4, 8, and 2.