I was wondering if it was possible to help me with finding different difficult methods to finding out the circumference and diameter of a broken plate if you only have half. I have used a method using perpendicular bisectors to find the middle of the plate and than times by two get the full diameter. I also plan on using pythagoras theorem.. These are not that advanced and would appreciate if I could get some suggestions if there any other methods I could use? 
Thank you!!
Thank you!!