NOTABUG.DOC, by Joseph K. Horn Cliff@evax9.eng.fsu.edu (Cliff Browning) writes: > If you want the 3rd. root of 125 you have to raise 125 to the 1/3rd. > power, and you get 4.9999999999... not 5. The way it was explained > to me by tech support is at HP was that the calculator solves the > fractional part of the power first and then raises the base number > to that power. > > To me I'd say that that is a bug. It is IMPOSSIBLE to raise 125 to the 1/3 power, because it is not possible to put 1/3 into the stack. You CAN put 0.333333333333000... (twelve 3's) into the stack, but that's not exactly 1/3, and that tiny difference is the cause of the "error". Using muMATH, I verified: 125 ^ 0.333333333333000 = 4.99 999 999 999 195 ... 125 ^ 0.333333333334000 = 5.00 000 000 001 609 ... Notice that a twelve-digit calculator cannot represent 1/3 any better than either of the above, and therefore 125^(1/3) cannot be calculated with any more accuracy than either option above. Of the two, the first is closer to 125^(1/3). It's what all 12-digit HP calcs yield. > Fortunately the 48sx has the XROOT() function which does give the > right answer. Exactly. Objecting that 1/X Y^X does not yield the accuracy of XROOT is as absurd as objecting that 1/X * does not yield the accuracy of / (try 153/17). So what? If you want a power, use Y^X; if you want a root, use XROOT. That's what it's for. Obtaining poor results through the misapplication of inappropriate functions is not a "bug". -Joseph K. Horn- -Peripheral Vision, Ltd.- New address: 19292 El Toro Rd / Silverado, CA 92676-9801 U.S.A.