Internal angles of a triangle

In this exploration, we will explore the internal angles of a triangle. Though it is one of the well-known properties of a triangle, a deeper exploration can lead to some interesting insights.

Exploring sum of angles


Why is the sum 180? How will you prove this analytically?

Inverted sum

When one of the angles are inverted what is sum? Why is it that particular value?

Parallel Lines

What fundamental property of parallel lines are we using in proving this?

Parallel line postulate

Will this property be valid when the parallel line postulate does not hold true?