A triangle is a polygon. It is a closed 3-sided shape made up of straight lines. The ‘tri-’ part of the word triangle means three. A triangle has 3 sides and 3 angles. Interior angles are the angles ...

vi) (Motivate) If a side of a triangle is produced, the exterior angle so formed is equal to the sum of the two remote interior angles. 2. Triangles i) (Motivate) Two triangles are congruent if any ...