Wikipedia has this proof with a few more intermediate steps: https://en.wikipedia.org/wiki/Proof_that_π_is_irrational#Niven's_proof https://en.wikipedia.org/wik

Wikipedia has this proof with a few more intermediate steps: https://en.wikipedia.org/wiki/Proof_that_π_is_irrational#Niven's_proof https://en.wikipedia.org/wiki/Proof_that_π_is_irrational#Niv.... That may be a bit easier to follow.