Piecewise Functions on TI Graphing Calculators
Date: 02/08/2005 at 22:06:50 From: Mark Subject: graphing piecewise-define functions on the calculator I was wondering if someone could tell me how to graph a piecewise- defined function on a TI-83 plus graphing calculator? None of the teachers in my high school know how to do it, and I have absolutely no clue how to do this.
Date: 02/08/2005 at 23:08:36 From: Doctor Peterson Subject: Re: graphing piecewise-define functions on the calculator Hi, Mark. I almost taught my class yesterday how to do this, but decided it wasn't worth the time it would take to explain it! It's a little tricky, and I was teaching some other tricky things already. Assuming you have the same TI-83 manual I do, look on page 17-4 where there is an example titled "Graphing Piecewise Functions". They don't really explain what they are doing, so I'll supplement it. Let's take a simple case: f(x) = -x if x < 0 x^2 if x >= 0 Since there is no "if" operation (as there is, say, in Excel or in C) for use within an expression, we use the fact that a logical comparison has a "Boolean" value (true or false) which in the TI-83 means 1 or 0. So the expression "x < 0" has the value 1 when x < 0 and 0 when x >= 0. Now, if we multiply -x by (x < 0), then when x < 0 we will get -x, and when x >= 0 we will get 0. We can do the opposite for the second piece of the function. Our piecewise function, as entered in the calculator, is then Y1=(-X)(X<0)+(X^2)(X>=0) Both comparisons are entered using the Test menu. For more pieces, the middle ones will use something like (X>5)(X<10) to express the interval from 5 to 10. If you have any further questions, feel free to write back. - Doctor Peterson, The Math Forum http://mathforum.org/dr.math/
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