# Homework Help: Graphically finding derivatives

1. Nov 6, 2007

### vanyel

1. The problem statement, all variables and given/known data
Determine the graphs for f' and f'' for each function y=f(x)

2. Relevant equations
y=(2^x)/((x^2)-1)

3. The attempt at a solution
I've been out of class for a while, and our textbook is hardly clear as to using nDeriv. I've tried entering in both y1=nDeriv((2^x)/((x^2)-1), x) and y1=nDeriv((2^x)/((x^2)-1), x, x) to graph f', but both result in a few seconds of a graph before spitting out err:argument (using a TI-83+). What am I doing wrong here?
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Nov 6, 2007

### SlideMan

^ Are you supposed to be using your calculator to graph them or plotting them on paper?

What's the graphical representation of the derivative of any curve?

3. Nov 6, 2007

### vanyel

we're supposed to graph them on our calculators, then sketch. not sure if that's what you were asking. I'm mostly wondering if the error is due to an incorrect mode or setting or something on the calculator, or if I'm entering the data in improperly.

4. Nov 6, 2007

### atqamar

I graphed y1=nDeriv((2^x)/((x^2)-1), x, x) and it came out fine. The window is set to standard.
By the way, when using the nDeriv function, here is how you set it up: nDeriv(function,variable,value)

If you are on the home screen, and you want to calculate the derivitive of a specific value to a decimal place, then add tolerance value in decimals at the end. nDeriv(function,variable,value,tolerance)

5. Nov 6, 2007

### vanyel

As I wrote in my initial message, I tried to graph exactly as you did. My window was set to Zoom standard. I tried this again, but again the same result came about: err:argument. Any ideas?