HP-71B Enhanced Math LEX
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01-26-2020, 03:08 PM
(This post was last modified: 01-26-2020 07:58 PM by Albert Chan.)
Post: #14
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RE: HP-71B Enhanced Math LEX
(01-26-2020 10:54 AM)J-F Garnier Wrote: The weakness of the z^2 operation in the HP71 Math ROM was mentioned in this article (last pages) of W. Kahan, now it is fixed! Thanks for the update ! Replacing Z^2 as Z*Z almost always give better result. It take a while to find a counter-example. >X=.254661579433 @ Y=.260740997689 >COMPLEX Z @ Z = (X,Y) >Z^2 (-3.13334783654, .132801428589) >Z*Z (-3.13334783655, .132801428589) Real part of Z = X*X - Y*Y = (X+Y) * (X-Y) gives better result. > (X+Y) * (X-Y) ! exact value = -3.13334783654 4934739232 -3.13334783654 |
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