# Proving 180° sum for interior angles of a triangle

- Author:
- JB Harrington

1. Create a triangle ABC (non-equilateral, non-isosceles)
2. Find midpoint of AB and label it D
3. Rotate triangle ABC 180° with D as the center
4. Find midpoint of BC and label it E
5. Rotate triangle ABC 180° with E as the center

How can you use this figure to prove that the interior angles of this triangle add up to 180°? Remember to write a clear and detailed explanation.