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Re: Different answers in mathematica and my calculator.

  • To: mathgroup at smc.vnet.net
  • Subject: [mg125595] Re: Different answers in mathematica and my calculator.
  • From: Bob Hanlon <hanlonr357 at gmail.com>
  • Date: Tue, 20 Mar 2012 02:23:20 -0500 (EST)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com
  • References: <201203191000.FAA01033@smc.vnet.net>

See tutorial/FunctionsThatDoNotHaveUniqueValues (or
http://reference.wolfram.com/mathematica/tutorial/FunctionsThatDoNotHaveUniqueValues.html
)

x == 4/(3 (-1)^(1/3));

This is a solution to

#^3 & /@ %

x^3 == -(64/27)

Solve[%]

{{x -> -(4/3)}, {x -> 2/3 (1 - I Sqrt[3])}, {x -> 2/3 (1 + I Sqrt[3])}}

-4/3 (-1)^(2/3) == 2 (1 - I Sqrt[3])/3 // Simplify

True

Solve[x^3 == -64/27, x, Reals]

{{x -> -(4/3)}}


Bob Hanlon


On Mon, Mar 19, 2012 at 6:00 AM, Nile <thrasher300 at gmail.com> wrote:
> 4/(3Power[2(-2)+3, (3)^-1])
>
> I get -(4/3) (-1)^(2/3) in Mathematica but only -4/3 on my calculator.
>
>
> N[Sec[8/(8 Sqrt[2])]]/Degree to get Cos^-1 of 8/(8 Sqrt[2]) and it gives me 75 deg instead of 45...
>
> I'm not sure what I'm doing wrong, I tried in Wolfram Alpha and it gives me the same thing.
>
> Thank you.
>
> -Francis
>



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