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Parametric tables for TI85
Posted:
Nov 9, 1997 5:45 PM


Someone was wondering how to use TI85 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((tMaxtMin)/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 exponentlooking 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



