Hi everybody...

I read some weeks ago (can't remember where), an inference to the TI-89 as a device which supplies "black box answers". Last week I downloaded a TI-89 emulator and have been dabbling with it. I will admit that it's implementation of AOS is quite good (better than other incarnations of AOS that I have used). For instance, when building an equation on the command line, one can venture up into the "history" stack as many time as needed to retrieve past items.

While looking at the graphing functions on the TI emulator, however, I think I may have found one of the "black box answers" referred to in the article I read. There is a "distance" function in the math menu of the graphing functions, which nicely gives the distance between 2 points on the graph. That would seem the be the end of it, however, (ie, the distance, the whole distance, and nothing but the distance) as I could see no way to get this figure out of the graphing environment, so it could be used in a follow on calculation. This would seem to hold true for the other graphing math functions as well.

By comparison, on an HP, there is no "distance" function, but of course distance is easily found by putting the cordinates of the 2 points on the stack and taking the difference, which gives a complex number that additionally contains direction as well (when viewed in polar form). This vector is now available on the stack, which is of course enormousley useful.

Before I pass jugement to quickly on this percieved black box functionality on the part of the TI, I thought I would tap the expertise which I know exists on this forum concerning some of the subtleties of running a TI-89 with the following question: Are the results obtained in the different environments on a TI-89 really as isolated (and seemingly unuseable in other applications) as it would seem, or am I missing a critical aspect of it's operation?