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

[Csaba Tizedes]

(12-15-2019 12:23 AM)Namir Wrote:  Repeating line 70 generates more error since that step has no theoretical justification. I did try it and the percent error jumped significantly!!!

Of course you must to store the temporary Euler estimation (YE) first:
50 D1=FND(X,Y)
60 X=X+H @ YE=Y+H*D1

Then use this, here the Y is totally same calculated as earlier:
70 Y=YE+H/2*(FND(X,YE)-D1)

We can repeat the calculation ("correction") of Y use the Euler estimation (YE) and the previously calculated, second order estimated Y:
75 Y=YE+H/2*(FND(X,Y)-D1)

Csaba