MathDB
f(x)/x=∞ for x->∞, integral is convergent of sin(f)

Source: VJIMC 2006 2.4

June 29, 2021
calculusintegration

Problem Statement

Let f:[0,)Rf:[0,\infty)\to\mathbb R ba a strictly convex continuous function such that limx+f(x)x=+.\lim_{x\to+\infty}\frac{f(x)}x=+\infty.Prove that the improper integral 0+sin(f(x))dx\int^{+\infty}_0\sin(f(x))\text dx is convergent but not absolutely convergent.