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Parametric tables for TI-85
Posted:
Nov 9, 1997 5:45 PM
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Someone was wondering how to use TI-85 to help students see limits
numerically. Having already done this on the 92 and 86, I thought it should
be doable on the 85, since I had revised a program from Marco Radzinschi
awhile ago to do normal tables.
The idea is to use geometric approach behavior for x so that F(x)
approaches its limit (if any) faster. One needs to define A and F(x) before
using the program and to set up the parametric editor.
Here's that program, one you run maybe once, and then save as a graph
database called LIM, which will need to be recalled before running the
table program. Also, the desired functions would need to be selected
afterward:
:xt1=A-.5^t
:yt1=evalF(F,x,xt1)
:xt2=A+.5^t
:yt2=evalF(F,x,xt2)
:xt3= -10^t
:yt3=evalF(F,x,xt3)
:xt4= 10^t
:yt4=evalF(F,x,xt4)
:FnOff
:0 STOREINTO tMin
:9 STOREINTO tMax
:1 STOREINTO tStep
:StGDB LIM
And here's the param table program, APTABLE:
:Param
:int((tMax-tMin)/tStep+1) STOREINTO K
:Disp K
:dimL eval tMin STOREINTO TC
:{K,TC} STOREINTO dim T
:For(t,tMin,tMax,tStep)
: li CONVERTTO vc eval t STOREINTO T(K)
:End
:T TRANSPOSE STOREINTO T
:For(I,1,TC,2)
: T(I)- SQUAREROOT(-1)*T(I+1) STOREINTO T((I+1)/2)
:End
:{TC/2,K} STOREINTO dim T
:T TRANSPOSE STOREINTO T
:Pause T
Here's an unnecessary program which might help define F and A correctly:
:InpSt "F(x)=",FS
:St CONVERTTO Eq(FS,F)
:Prompt A
:Disp "Select functions,"
:Disp "then run APTABLE."
It is unnecessary because F and A can easily be defined on the home screen:
F=sin x/x
0 STOREINTO A
APTABLE
STOREINTO is the "store arrow", above the ON key.
TRANSPOSE is the "little T exponent-looking thing" found in MATRIX MATH F2.
And CONVERTTO is the "filled in triangle" which is part of the LI>VC and
ST>EQ commands which are found in LIST MORE F4 and STRING F5.
I think I'll store this on my web page,
http://www.geocities.com/capecanaveral/lab/8692,
as a zipped group file (APTABLE.85G) in case anyone wants it.
Ah, what fun it was!
Dave Slomer
AP Calculus and computer science teacher
Winton Woods HS, Cinti, OH 45240
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