I thought this one was obvious. The man who invented pi was one of the members of King Arthur’s Court. He was the one who invented the roud table, Sir Cumference. 
Naw, bibliopahge was right that it was a woman who invented pi. Specifically, my grandmother. Or if she didn’t invent it, she certainly did a great deal to develop the idea and popularize it. Why no mention of her, bib?