What good is a sophisticated graphing calculator without a host of useless tricks to amaze your friends with?

No, it's rhetorical. Don't bother answering.

Here's one to start off. This trick relies on the finite granularity of the TI family. First, let's get some simple algebra straight:

     x + 69 - x = y

y will always be 69, right? If you assign some random value for x and enter the expression on the left in your calculator, it will indeed come out to 69. Unless...

...you assign x to be some arbitrarily large number, e.g. 10^99. If you do this, and enter the expression into your calculator, you'll find that y = 0. What gives?

The enormous value of x is stealing the thunder of the constant 69. As the TI only deals with the 14 or 15 most significant digits of the value at hand, everything smaller is thrown out with the bath water.

I know for many of you this is probably petty and less than amazing, but I remember getting a kick out of it back in the day and thought I'd share.