From, well, the tail of an ox. It couldn't be any simpler. Quora probably will tell me this will collapse because it's too short, so: it's very common in Brazil's countryside. It's fat (too fat for me, not my favourite food), but healthy.
We can divide octagon into six triangles. So, the sum of the angles of each triangle is 180 degrees. For octagon, the sum of the interior angles is 1080 degrees and there are eight sides. Let us make a circle in the middle of the octagon and measure the central angle of a regular octagon. A circle is 360 degrees around.
This is an octagon. An octagon has 8 angles, 8 sides, and 8 vertices. An octagon looks just like a stop sign.