# Internal angles of a triangle

- Author:
- damitr

- Topic:
- Angles

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

## Proof

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?