Calculators Log key for ti-89

1. Sep 22, 2005

philipc

I have a class where I'm using the log function a lot, I would like to program a hot key to display log on my ti-89 for I don't have to mess with the catalog, any suggestions?
Thanks
Philip

2. Sep 22, 2005

Jameson

There isn't a nice key for base 10 logs. Use the change of base formula, using natural logs.

$$\log_{a}b=c$$

$$a^c=b$$

$$c=\frac{\ln b}{\ln a}$$

EDIT: Sorry, you wanted to program a hotkey. I'm not familiar with how to do that, but I'm sure it's in the manual.

Last edited: Sep 22, 2005
3. Sep 23, 2005

philipc

I know how to program the hot keys, but it displays only in the program window, if I can display it in the main window, I would be set. Any one know how to make a program display stuff in the main window?
Thanks
Philip

4. Sep 23, 2005

shaner-baner

if you want to use this function in calculations, a program isn't very helpful. I would suggest a user defined function. first,let me mention that I think log is in catalog, maybe you can move it to your custom menu. Anyways, what I do, is make a function that does the log base anything of anything. try this: define Logg(a,b)=ln(b)/ln(a) or you could do ln(b)/ln(a)-> Logg(a,b) (ps the '->' is the store button on your calculator. I think define is f4 or something, if you can't find it look in your catalogue)

5. Sep 23, 2005

philipc

Can you enlighten me on this custom menu stuff
Philip