1. Triangle Sum Property Theorem
The sum of the measures of the interior angles of a triangle is 180o. 3 2 1
∠1 + ∠2 + ∠3 = 180°

2. The sum of the measures of the interior angles of a triangle is 180o.
Property of triangles
The sum of the measures of the interior angles of a triangle is 180o.
60º
90º
30º +
60º
180º
30º
90º

3. The sum of the measures of the interior angles of a triangle is 180o.
Property of triangles
The sum of the measures of the interior angles of a triangle is 180o.
60º
60º
60º
60º +
180º
60º
60º

4. Example: Can 100°,120°be any two angles of a triangle? Solution :
Sum of the given angles is 100°+120°= 220°. This is greater than 180°, but the sum of the measures of the angles of a triangle should always be 180°. Even though the third angle is not known it is not possible to form a triangle with the given measures.
Therefore a triangle cannot have two obtuse angles.

5. Can we draw a triangle using the given angles? 80O , 60O , 70O
Try These:
Can we draw a triangle using the given angles?
80O , 60O , 70O
45O , 55O , 80O