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.
An equilateral octagon will have 8 equal internal angles and would be
Each internal angle is 135°.
But the interior angles would still add up to 1080°.