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What's the calculator doing? (Posted on 2019-03-06) Difficulty: 3 of 5
If I plot Y=sin(95X) on my TI-84 plus silver edition with window settings Xmin=0, Xmax=2π, the graph looks exactly like the regular sine function Y=sin(X).

If you graph the same thing on a TI-84 plus CE calculator however, they do not look the same. Instead you have to make a graph of Y=sin(133X).

What are these calculators doing? What difference between the calculators does this reveal?

No Solution Yet Submitted by Jer    
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Solution solution | Comment 1 of 4
On the TI-84 Plus Silver Edition, when the Xmin is set to 0 and Xmax to 2*pi, the deltaX is .0668423968; this is also the change in x when, during a trace, the right movement key is pressed, unlike in the CE.

On the TI-84 Plus CE, when the Xmin is set to 0 and Xmax to 2*pi, the deltaX is .023799944344697, which is 2*pi/264. Presumably that's a result of there being 265 possible x-value columns of pixels. I don't know why this is the case as the screen resolution is advertised as 320x240 pixels. But in any case, when showing y=sin(95x), the next value after x=0 is for x=95*2pi/264 or about 2.26 radians (I'm sure you're in radian mode). That's considerably far into a cycle of the function. If, however, you plot sin(133x) the next value according to the deltaX would be just one deltaX value above pi, and that would give a negative sine value. It would seem the calculator is using twice this deltaX value, which it labels the TraceStep.

It doesn't seem as if the deltaX has any effect on the plotting--just the TraceStep.

  Posted by Charlie on 2019-03-06 15:26:51
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