Ninja of the North wrote:In my opinion, if you are looking for an upgrade from a TI 82/83, go for the 89. I find that the best feature of it is that it will display exact values, i.e. radical 2 instead of a decimal, pi/4 instead of 0.7853975 (very handy if trig is not your forte).
Not exactly. It has two different types of numbers: rationals and floats. Rationals are the ratios of two integers, and the integers can be very long. Floats are fixed-length binary
approximations. When you type in "1.5", it is read as a float. When you type in "3/2", it evaluates to a rational, 3/2.
If you ask the TI-89 for the square root of "2", it will display radical 2. If you ask it for the square root of "2." or "2.0", it will display 1.41421356, because it doesn't want to waste time being exact when dealing with floats, which are inherently approximate.
Also, floats are contagious. "2.0 * 3/2" gives "3.0", while the non-float-infected "2 * 3/2" gives "3".
These are subtle issues, but it's important to know about them if you intend to use a TI-89 seriously. Or program computers, for that matter; it's shocking how many CS students don't understand floating-point arithmetic.