fact: Definition W_even n := ((PI/2)*(fact (2 * n))/(2 ^ (2 * n) * (fact n) ^2 )).
imports: PeanoNat Reals Rintegral Rintegral_usual Rintegral_tactic Lia Lra Rsequence_facts Rsequence_subsequence Rpser RTaylor MyRfunctions Rsequence_tactics