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effort
Senior Member

USA
38 Posts

Posted - 02/10/2012 :  10:14:38  Show Profile  Reply with Quote
I am trying to graph the following on a TI-84 plus:

1. y = -(x-1)+1 0x2, 0y1



2. y= -(x+1)+1 -2x0, 0y1



3. y = x-4, -2x2, -4y0


The graph is suppose to be a picture of a heart. I know how to restrict the domain by typing in the function into y = and then /(my domain). I just can't figure out how to restrict the range. I have even played with the window but the picture isn't what the teacher is expecting. Please help.
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the_hill1962
Advanced Member

USA
1468 Posts

Posted - 02/13/2012 :  15:48:38  Show Profile  Reply with Quote
Restricting the domain is all that needs to be done.
Using the logical "and" function will accomplish this.
You see, that function results in either a "1" or "0".
Here is the truth table for the "and" function:
0 and 0 = 0
0 and 1 = 0
1 and 0 = 0
1 and 1 = 1
So, if you were to multiple your equation by the appropriate "and", it would come out to be 0 (and essentially be invisble on the graph since it plots on the x-axis) in the first three cases and it comes out to be the value of the function in the 4th case since multiplying by "1" just gives that value.
Now, these "1" and "0" are truth values.
I don't know how much you know about this but here is what you would put for 0x2:
(x0 and x2)
You see, for 0x2 makes "x0" true "1" also "x2" is true "1". 1 and 1 is 1 so for that interval you multiply by 1.
Outside the interval makes either part false and thus multiple by 0 and the value is 0 so it won't show on the graph.
Here is what you type into the calculator:

Y1=(-(x-1)+1)*(x0 and x2)
Y2=(-(x+1)+1)*(x-2 and x0)
Y3=(x-4)*(x-2 and x2)

You can graph this on the standard 10x10 window (by pressing ZOOM then option 6 ZStandard. Or, it looks nice if you use the following window then press graph:
Xmin=-5
Xmax=5
Ymin=-7
Ymax=1

You may have questions because I didn't go into detail about all that I have said here. Let us know if you want more detail about any of the above.
BTW, I don't believe that you can restrict the range with the graphs other than by setting the window. You didn't need to worry about restricting the range for your problem because the teacher already chose the appropriate domain that makes the graphic come out.

Edited by - the_hill1962 on 02/13/2012 16:05:03
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effort
Senior Member

USA
38 Posts

Posted - 02/14/2012 :  09:41:57  Show Profile  Reply with Quote
Thank you so much....your explanation is perfect.
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