MathDB
Today's calculation of Integral 306

Source: 2008 Tokyo Institute of Technolgy entrance exam 1st Round, Problem 1

February 26, 2008
calculusintegrationfunctionlogarithmsgeometryalgebradomain

Problem Statement

For positive real numbers a, b a,\ b, two graphs of the function : xa x^a and lnbx \ln bx have a tangency of point. (1) Let (s, t) (s,\ t) be the tangency of point, express this in terms of a a, then express b b as the function of a a. (2) For h h with 0<h<s 0 < h < s, denote the area as A(h) A(h) of the domain bounded by the line x \equal{} h and two curves y \equal{} x^a,\ y \equal{} \ln bx. Express limh0A(h) \lim_{h\rightarrow 0} A(h) in terms of a a.