# WHY must a pentagon add up to 540° (in pictures)

Because there are now 3 triangles in a pentagon, it must add up to 3times180°=540°

The pentagon can be made from 3 triangles.

Example 1

An equilateral pentagon will have 5 equal internal angles and would be

540^circ/5=108^circ

Each internal angle is 108°.

But the interior angles would still add up to 540°.