(Free42) roundoff for complex SQRT

04092018, 08:22 PM
(This post was last modified: 04092018 08:27 PM by Dieter.)
Post: #11




RE: (Free42) roundoff for complex SQRT
(04032018 01:28 PM)Werner Wrote: Free42 shows 2+i2, which SHOW reveals to be really 2+i(21E33). I assume (!) that the reason why a physical 42s returns an exact result simply is its three guard digits: the function is calculated to 15 digits, and if this yields 2,00000000000012 + 1,99999999999996 i this does not become visible as it is rounded to 12 digits before it is returned to the user. I wonder if Free42 (or DM42) make use of such guard digits. Is it possible that here these calculations are performed with the same 34 digits that are finally returned? This would explain slight errors in the last digit. Or are there really some additional digits that would cover roundoff errors like the ones discussed here? Edit: I just noticed that the use of guard digits has already been mentioned in your later post. Dieter 

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