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Accurate x - log(1+x)
04-04-2023, 11:05 PM (This post was last modified: 02-02-2024 04:52 PM by Albert Chan.)
Post: #6
RE: Accurate x - log(1+x)
I added HP71B implementation of log1p_sub(x), called FNL(X)
https://www.hpmuseum.org/forum/thread-19...#pid170860

Update 2/02/24: FNL recursion part is not necessary
see https://www.hpmuseum.org/forum/thread-21...#pid183567

(02-02-2024 04:27 PM)Albert Chan Wrote:  FNL(X) recursion replaced with direct fast-path:

200 DEF FNL(X) ! = ln(1+X) - X, but more accurate
210 IF X<-.3832 OR X>.5163 THEN FNL=LOGP1(X)-X @ GOTO 250
220 X2=X/(X+2) @ X4=X2*X2
230 X4=X4*(5005-X4*(5082-X4*969))/(15015-X4*(24255-X4*(11025-X4*1225)))
240 FNL=X2*(X4+X4-X)
250 END DEF
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Messages In This Thread
Accurate x - log(1+x) - Albert Chan - 05-05-2022, 07:52 PM
RE: Accurate x - log(1+x) - Albert Chan - 05-05-2022, 08:18 PM
RE: Accurate x - log(1+x) - Albert Chan - 05-05-2022, 08:57 PM
RE: Accurate x - log(1+x) - Albert Chan - 05-06-2022, 02:03 PM
RE: Accurate x - log(1+x) - Albert Chan - 05-09-2022, 12:41 AM
RE: Accurate x - log(1+x) - Albert Chan - 04-04-2023 11:05 PM



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