Mathematics for IGCSE & O level - Angles (Section 3 - No. 50)
Which of the following statements is true about the exterior angle of a triangle?
It is always less than 90 degrees.
It is always equal to one of the interior angles.
It is always greater than 90 degrees.
It is equal to the sum of the two opposite interior angles.
Explication
The exterior angle of a triangle is equal to the sum of the two opposite interior angles.