兩邊各取兩次對數 ln 得: pi vs. e*ln(pi) + ln(ln(pi))
define function
f(x) = e*ln(x) + ln(ln(x)) - x
f(e) =0. Try to get f(pi) > 0
easy to get f'(x) > 0 when x>e
所以原式左邊較小右邊較大