# WHY must a heptagon add up to 900° (in pictures)

Because there are now 5 triangles in a heptagon and it must add up to 5times180°=900°.

The heptagon can be made from 5 triangles.

Example 1

An equilateral heptagon will have 7 equal internal angles and would be

900^circ/7=128.57^circ

Each internal angle is 128.57°.

But the interior angles would still add up to 900°.