torture test: powers & roots
round #2
this test it to compute the cube root of -27 for which -3 is expected. of course, this is just one of the 3 cube roots of -27. the others being 3/2 +/- 3i*sqrt(3)/2.
the second test i planned was (-32)^(3/5) which is -8 real and two complex roots. however no machine found the real root straight from the ^(1/3) or cube root (if present) functions. the Ti-89 offered the correct but unexpected symbolic answer of -2*(sqrt(5)-1) + i*2*sqrt(2*sqrt(5)+5) but not its conjugate.
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the casio fx-991es gives (-32)^(3/5) as -8, the principal solution. |
| calculator | displayed result |
| hp15c | Error 0 |
| hp30s, hp9g | -3 |
| hp28c, hp48g | -3 (using nth root function) , (1.5,2.59807621135) otherwise. |
| hp32sii | -3 (using nth root function), INVALID y^x otherwise. |
| hp20s | Error - Func (using y^x, there is no nth root function). |
| hp35 | 0 (flashing) |
| casio fx-190 | -3 |
| casio fx-19, fx-29 & fx-39 | E |
| casio fx-120 | E (using x^1/y button) |
| casio fx-82, fx-82l, fx-350 | -3 (using the built-in cube root function) (E using x^y) |
| casio fx-100, fx-3500p, fx-180p | -3 |
| casio fx-300h, fx-85v, fx-85m, fx-920 | -3 |
| casio fx-4000p, fx-3900pv, fx-992v, fx-5500l, fx-451m | -3 |
| boots 425 | E |
| sharp el-512, el-531p, el-5020 | -3 |
| sharp el-9900 | -3 |
| commodore sr4148r & 1540 | E (despite having a nth root button) |
| national semiconductor 4640 | Error |
| sinclair enterprise | Error |
| ti sr-50, ti-55, ti-51-III, ti-58, ti-59 | 3 (flashing) |
| ti-52 | -3 |
| ti-30, ti-30s | Error |
| casio fx-991es, fx-570es | -3 |
| sharp el520w | -3 |
| ti-89 | 3/2+i*3*sqrt(3)/2 (symbolic answer) |