Textbook Problem

Analyzing a Function In Exercises 75-80, use a graphing utility to (a) graph f and f’ in the same viewing window over the specified interval, (b) find the critical numbers of f, (c) find the open interval(s) on which f' is positive and the open interval(s) on which f' is negative, and (d) find the relative extrema in the interval.

Function

Interval

$f(x)=\left(\ln x\right)\text{cos }x\left(0,2\pi \right)$