Fundamental properties of triangles.

The sum of internal angles of a triangle is equal to 180:

An exterior angle of traingle is equal to the sum of the interior angles no adjacent to it

EXERCISES

1. In the figure find X

    

a) -6°           b) -8°          C) -10°         d) -20°             e) -62°

We know that the sum of the interior angles of triangle is equal to 180°, so:

2. In the figure find X

                                    a) 39°         b) 52°         c) 61°         d) 121°         e) 102°

We know that the measure of an external angle is equal to the sum of the interior angles not adjacent to it, so: