A stop sign has the shape of a regular octagon. What is the sum of the interior angles of a stop sign?

2 Answers
Dec 24, 2015


Use the interior sum formula ..


Sum #=(n-2)xx180=(8-2)xx180=1080^o#

hope that helped

Apr 30, 2016


The sum of the interior angles can be calculated easily by understanding where the formula comes from.

For an octagon: Sum = #180 xx 6 = 1080°#


In any polygon, you can divide it up into triangles by joining one vertex to all of the others. You will find that the number of triangles is ALWAYS 2 less than the number of sides.
ie 3 sides gives 1 triangle. 6 sides gives 4 triangles, 10 sides gives 8 triangles and so on..
But, the sum of the angles in any triangle is always 180°.

So, subtract 2 from the number of sides and multiply by 180°.

This is exactly what #180(n-2)# tells us, but it is really nice to understand why that formula works. You will never have to learn the formula if you understand it.

An octagon has 8 sides, which means #6# triangles.

So the sum of the interior angles is:

#180 xx 6 = 1080°#