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RE: HP48-HP50G : Error functions ERF(z), FRESNEL integrals, PROBIT, etc.
11-12-2023, 04:25 PM
Post: #19
Albert Chan Offline
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RE: HP48-HP50G : Error functions Erf(x), Erfc(x) & Erf/Erfc —>x
(11-11-2023 11:34 PM)Gil Wrote:  The erf function of the HP Prime, however, gives all the digits correct.
Does somebody know how (which algorithm) the HP Prime proceeds to obtain such a performance?

For small argument, erf(x) = 2/√(pi) * x * hyp1f1(1/2, 3/2, -x*x)
For large argument, erfc via continued fraction. (erf from erfc very accurate!)

see https://www.hpmuseum.org/forum/thread-15...#pid135589
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RE: HP48-HP50G : Error functions Erf(x), Erfc(x) & Erf/Erfc —>x - Albert Chan - 11-12-2023 04:25 PM



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