# WHY must an octagon add up to 1080° (in pictures)

Because there are now 6 triangles in an octagon, it must add up to 6times180°=1080°

The octagon can be made from 6 triangles.

Example 1

An equilateral octagon will have 8 equal internal angles and would be

1080^circ/8=135^circ

Each internal angle is 135°.

But the interior angles would still add up to 1080°.