# Homework Help: Finding invertible complex function

1. Mar 1, 2009

### gzAbc123

Hi there,
This is my first time posting on this site. I'm doing Calculus 2 and am stuck on finding whether or not the following functions are invertible in the given intervals and explaining why.

(a) sechx on [0,infinity)

--> I solved (a) but (b) and (c) is where I'm stuck.

(b) cos(lnx) on (0, e^pi)

(c) e^(x^2)

Can someone please help?

2. Mar 1, 2009

### Tom Mattson

Staff Emeritus
You don't have to find the inverse function, you just have to determine if an inverse exists. A necessary condition for invertibility on an interval is that the function is one-to-one on that interval. This condition is met if the function is monotonic on the interval.

So how would you determine whether a function is monotonic on $[0,\infty)$?

3. Feb 17, 2011

### mancini0

A function is monotonic if it is strictly increasing or decreasing, correct? Then one would find this info out based on the sign of the first derivative?

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