Explain the triangle angle sum property and how it can be used to determine the measure of angles.

The Triangle Angle Sum Property
 The Triangle Angle Sum Property says that the sum of its internal angles is 180°. If A, B and C are the internal angles of the triangle, then: A+B+C = 180°.

 How it can be used to determine the measure of angles?
 For example, if you have a triangle with internal angles A, B and C (A=50° and B=40°), but you don't know the value of the angle C, you can calculate it using The Triangle Angle Sum Property, as follow:
 
 A+B+C=180°
 C=180°- A - B
 C=180°- 50°- 40°
 C= 90°