Dear PF FOrum, I have a question about Pi. In some Youtube videos, they explain why the volume of a sphere is so,... Why the area of a sphere is so,... Why the area of a circle is so,... All are good explanations, with or without differential. But I can't find the proof why Pi is 3.14. I have searched google (and Youtube). The best that I have is Archimedes tried to divide a circle into 96 slices. Is there any math proof why Pi is Pi? Perhaps like regression number? Thanks for any idea.