What is the sum of the angles at the blue vertices of this 11-gon?
Scroll down for a solution to this problem.
Solution
The sum of angles is 900°.
Solution by Matthew Arcus: 11 turns, adding up to 6π, since we go round 3 times, each turn is π-α where α is the vertex angle, so 11π – ∑α = 6π, so ∑α = 5π = 900°.