MathDB
Ratios of areas: Arch and Triangle

Source: 2020 CIIM P1

October 31, 2020
analytic geometryalgebra

Problem Statement

Let α>1\alpha>1 and consider the function f(x)=xαf(x)=x^{\alpha} for x0x \ge 0. For t>0t>0, define M(t)M(t) as the largest area that a triangle with vertices (0,0),(s,f(s)),(t,f(t))(0, 0), (s, f(s)), (t, f(t)) could reach, for s(0,t)s \in (0,t). Let A(t)A(t) be the area of the region bounded by the segment with endpoints (0,0)(0, 0) ,(t,f(t))(t, f(t)) and the graph of y=f(x)y =f(x). (a) Show that A(t)/M(t)A(t)/M(t) does not depend on tt. We denote this value by c(α)c(\alpha). Find c(α)c(\alpha). (b) Determine the range of values of c(α)c(\alpha) when α\alpha varies in the interval (1,+)(1, +\infty).
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