how to measure a circle. As we all know we can measure a line with a scale or any instrument but right now I have studied circles and was wondering if there was any way , instrument or method to measure circle i.e the circumferrence without the formula $2πr$. 

To measure the circumference of a circle without using $C = 2πr $ you need to find a way to make it linear. This can be done by simply wrapping a string around the circumference, cutting it to make it the correct length, then measuring the length of the string.
