Dear Sarva,

The calculation of Pi is part of the evaluation of nonlinear function, that's why I propose to you to consult links as well as the attached files.

-Numerical evaluation — SymPy 1.1.1 documentation

docs.sympy.org/latest/modules/evalf.html

-How do we calculate an irrational number with high precision ...

https://www.quora.com/How-do-we-calculate-an-irrational-numbe...

Best regards

Thank you

I think one simple reason is that the value of \pi was first used to get the perimeter/area of a circle only and that has nothing to do with pythagorus theorem.

Dear scholar

here is a truth

Thank you.