... I didn't insult you. I simply stated that fourth graders are taught this very equation and that as such, it is common knowledge. You can dispute the equation all that you wish, but it still stands that A = пr² ...
You're confusing the formula for the area of a circle (A = пr²) - which was never in doubt or even a question, BTW ... with cross-sectional-area:
, but I'm through quibbling.