. "proofs that is irrational" . . "Lambert's proof" . "Proof that \u03C0 is irrational" . . . . . "first to prove being irrational in the 1760s" . . "elementary proof that is irrational" . "elementary proof of the irrationality of" . . "proof that \u03C0 is irrational" . "irrationality of" . "Proof that is irrational" . "prove that \u03C0 is irrational" . "proof that is irrational" . "Proof that \u03C0 is irrational" . .