Some of you asked about taking a derivative on an 84 today.  If you have a TI84 CE (see image below), you can!  Not on a regular TI84, but a TI84 CE.

You may first need to update your TI OS HERE. and you will need the TIConnect  software to update it.

Then go to TICalcWiz you will have to download the .zip file and upload it with the TIConnect  software.

So there are many steps and you have to decide if it is worth your while.

In addition, I have not tested it and I take no responsibility for your calculator, if it bricks. TiCalcWiz, I believe it a fairly good site.