(71B) Euler-Taylor method for the HP-71B

[Namir]

Thanks Albert for providing approximations for the seocnd and third derivative to extend the original Euler method.

If Albert ever attends an HHC conference then I am buying him dinner on Friday night (the eve of the start of the conference) OR Sunday night (where the HHC attendees go out for dinner). I am good for my word!

Here is an update of my original listing to take into account Chan's suggestions.

Code:

10 REM EULER-TAYLOR WITH 3 DERIVATIVES
20 DEF FNX(X,Y)=X*Y
30 FNE(X) = EXP(0.5*X^2)
40 READ A, B, Y, H
50 DATA 0, 1, 1, 0.01
60 N=INT((X1-X)/H+.5)
70 X=A
80 FOR I=1 TO N
90 D1=FNX(X,Y)
100 X=X+H @ Y=Y+H*D1
110 D2=H/2*(FNX(X,Y)-D1) @ Y=Y+D2
120 IF I>1 THEN Y=Y+(D2-D3)/3
130 D3=D2
140 NEXT I
150 Y1=FNE(B)
160 DISP "Y =";Y
170 DISP "Y EXACT=";Y1
180 DISP "%ERR =";100*(Y-Y1)/Y1
190 END