Copyright © University of Cambridge. All rights reserved.

'Outside the Nonagon' printed from http://nrich.maths.org/

Show menu


The diagram shows a regular 9-sided polygon (a nonagon or an enneagon) with two of the sides extended to meet at the point X.

What is the size of the acute angle at X?




If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.

 

This problem is taken from the UKMT Mathematical Challenges.

View the previous week's solution
View the current weekly problem