4 replies to this topic

[Stian]

Hey
I have the Casio fx9860GII and i need to know how to enter piecewise defined functions, with use of x greater than, equal or less than.
I am aware of the brackets, but i know that texas instruments make use of the alligator-mouth-signs, but i have not found them on casio and you can`t make a piecewise defined function without them.. like this

f(x) = x if x < -1
f(x) = 3 if -1 ≤ x ≤ 2
f(x) = -x if x > 2

can someone show me how to enter this into my calculator and get a correct graph?

[3298]

There are two methods for this:
1. On Casio calculators you can use the fact that a condition evaluates to 1 or 0, so you can put parentheses around the condition, multiply it with something else, and then add such terms together. Take care that these do not overlap, otherwise you get unwanted results.
Your example function thus becomes X(X<-1)+3(-1<=X And X<=2)-X(X>2). Pretty straight-forward. Mind that on Casio calculators you need to hunt down every single token in menus, trying to write them letter by letter will result in the message "Syntax ERROR". Also, the subtraction and negation are different. Both are on the keyboard, the one in parentheses ((-)) is the negation one.
Unfortunately this trick seems to be not intended; the Graph menu has no menu with comparison tokens. You'll have to go the long route and write the entire formula into the Run menu with quotation marks around it, followed by the assignment arrow, a special Y symbol (printed in bold on newer calculators; to be exact, from the Algebra FX series on) and a number from 1 to 20 telling the calculator the slot to store the formula into. You find the special Y symbol in the menu reached with the VARS button.
Now you have the formula in the list in your graph menu, so you can draw it as usual. Note that differentiation and integration maight give wrong results when dealing with graphs that have corners or steps.

2. You can give graphs a range parameter. I haven't found this in a manual yet (in fact, that was the only thing I learned from my math teacher about the calculator), and I haven't tried this on newer calculators. But this is the syntax: <function>,[<min>,<max>] makes the function only get drawn from min to max. You need the comma and the square brackets, all of them are on the keyboard, so you can enter this directly in the Graph menu. I think you can't set min or max to infinity, so when you want to use only one of them, simply set the other to some really high value like 9.E99 (of course negative for min).

[scientifix]

What you can also do is using this for example :
Y=x^2, [3, 50]

By adding [number, number] you define the function on a a range.

[3298]

... which I listed as solution 2. You're too late.

[ehsanhee]

how can i put LESS THAN or "<" sign into this calculator? thanks a lot.