The figure is made up of three semicircles. The line through $O$ divides the perimeter of this figure into two parts.

What can you say about the lengths of these two parts as you move the points $P$ and $O$?

Created with GeoGebra

NOTES AND BACKGROUND

You might like to download your own free copy of GeoGebra from the link above and draw this dynamic diagram for yourself. You will find it easy to get started on GeoGebra with the Quickstart guide for beginners.