MathDB
Today's calculation of Integral 750

Source: 2011 Tsukuba University entrance exam

August 31, 2011
calculusintegrationlimitlogarithmscalculus computations

Problem Statement

Let an (n1)a_n\ (n\geq 1) be the value for which x2xetndt (x0)\int_x^{2x} e^{-t^n}dt\ (x\geq 0) is maximal. Find limnlnan.\lim_{n\to\infty} \ln a_n.