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General Discussion Board \ Math Help \ TI89: cube root of -1

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AuthorComment
erdeky
Probe
Posted: 8 Jul 2011
09:50 GMT
Total Posts: 6
Is there a way to make (-1)^(1/3) display -1 instead of 1/2 + (sqrt(3)/2)i ?
haveacalc
Guardian
avatar
Posted: 10 Jul 2011
23:15 GMT
Total Posts: 1111
Do you want it to show the result as an expression, e.g. 3√ ̅-1̅, or are you looking to intentionally display an incorrect answer?

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erdeky
Probe
Posted: 11 Jul 2011
08:00 GMT
Total Posts: 6
Not looking for that expression, but

since (-1)^3 = -1, I am looking the real cube root of (-1) and not the principal one which the TI-89 gives.

I see that in the TI-89 ( (-1)^(1/3) )^3 = -1.

Joe
haveacalc
Guardian
avatar
Posted: 12 Jul 2011
21:21 GMT
Total Posts: 1111
It sounds like you're aware that roots of negative numbers are often complex, having both a real and an imaginary part. If you haven't done so already, you'll need to set your calculator to accept complex numbers by pressing the [MODE] button and changing the complex format option to rectangular.

If you're looking to get the real and complex parts separately, use real( and imag(.

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