# Graphing calculator find an eqn?

1. Dec 25, 2004

### aisha

Find Equation On Graphing Calc Plz Help!!!

I know how to graph the inverse on the t1 83 graphing calculator
u press 2nd prog 8 y vars enter but Is there a way to find the eqn of the inverse after its graphed???

HELP SOMEONE PLEASE THIS COULD MAKE MY LIFE SOOOO EASY PLZ PLZ PLZ HELP ME!!!!

Last edited: Dec 25, 2004
2. Dec 25, 2004

### Parth Dave

I don't think there is. But if you are required to find the inverse, then you can use the DrawInv function to check your answer. Simply draw the inverse, and then plug in your equation into another Y. If the two match then you did it correctly.

3. Dec 25, 2004

### aisha

Thats what I do know how to do DrawInv but I wanted to know a way to find an equation for that inverse line using the graphing calculator

4. Dec 25, 2004

### Parth Dave

Yea, I'm pretty sure you can't.

5. Dec 26, 2004

### Tom McCurdy

lol remind me how to, and I will write a program for the TI-83 that does it

6. Dec 26, 2004

### Tom McCurdy

hmm I mean i know how to take an inverse of a fuction, what I am asking is are you only using one paritcular type... linear, exponetial... or do u need a general program

7. Dec 26, 2004

### Justin Lazear

With an 83, your best bet is to graph the inverse and then try to fit an equation to that graph. Unfortunately for you, you have to guess what kind of fit to try, and there are only a limited number of equations the 83 can fit to.

All in all, you're just going to have to make your life easy by learning how to get inverses on your own.

--J

8. Dec 26, 2004

### Parth Dave

For the most part it is more working trying to graph it and then fitting something. If you know how to solve for the inverse, that is usually easier.

9. Dec 26, 2004

### Justin Lazear

In fact, even if you don't know how to solve for the inverses, it'd be easier to learn than go through all the trouble of trying to convince the 83 to do it.

The 83 simply doesn't have the right tools for symbolic algebra.

--J

10. Dec 27, 2004

### aisha

lol I have learned how to find out the inverse myself, but sometimes I just want to be 100% sure and when my equation in y= does not fit the DrawInv line I wish the calc would just tell me the equation of the line. If its possible to make a program of course I would love it, but would need it for general problems u never know what the teacher will give u lol.

11. Dec 28, 2004

### Justin Lazear

Have a little faith in yourself. Also, you can check yourself with the

$$f^{-1}(f(x)) = x$$
and
$$f(f^{-1}(x)) = x$$

identities.

And either way, a few wrong answers won't kill you. The important part is getting the idea.

--J