How do I use triangle sum properties to find unknown values?

One way to be able to use the triangle some properties to find unknown values can be by being able to classify a triangle either by its sides or angles. For example some of these trianlges that are classified by its sides are scalene which have no congruent sides, isosceles, at least two congruent sides and the equilateral triangle which all three sides are congruent and some of the triangles that are classified by angles are the acute, obtuse,equiangular and right triangles. They all share a vertex. Such angles are equal in measure and can be described as congruent. Also something important you should remember is that the sum of the three angles in a triangle is always 180 degrees, A+B+C=180. Exterior angles of triangles- Angles that form linear pairs with the interior angles. Some of the different terms when you are lokking for trinagle sum properties are Interior Angles Of triangles, Triangle Sum Therom, Corollary, and the Exterior Angles Therom.