How do you do a cube root on a TI-89? (1 Viewer)

[Scott Burke]

I have looked through the instruction manual, but I cannot figure out how to do it. Anyone know?

 

[Daryl Furkalo]

I have a TI-85, so how about ^1/3? Should be right.

 

[BrianW]

Alternatively, you could follow these steps:
Enter the number you want to find the cube root of.
Press the [ INV ] key.
Press the [ x^y ] key.
Press the [ 3 ] key (or enter any root value you want).
Press the [ = ] key.
Your answer will be in the display.
Doing Inverse-Power is the same thing as finding a root.

 

[Joe D]

The easiest way to do this is to take x to the (1/3) power. Instead of a cube root.

 

[BrianW]

The easiest way to do this is to take x to the (1/3) power. Instead of a cube root.

How is this easier? Unless there's something I'm missing, this method takes more keystrokes - parenthese, even, to get the 1/3 or invert a 3 - than doing a cube root.
Is there something I don't know?

 

[Artur Meinild]

Brian, in some funny way you contradict yourself. What you suggested in the previous post *was* to take x to the 1/3 power...
It's just a matter of the easiest combination of keystrokes - on a HP calc, the easiest way would be [3] [INV] [X^Y]...

 

[BrianW]

Brian, in some funny way you contradict yourself. What you suggested in the previous post *was* to take x to the 1/3 power...

Ah, so we're talking about mathematical equivalence, not whether using the [ INV ] key simplifies the process... I get it now. Thanks.

 

[Bill Catherall]

One more reason to own an HP 48G. We get a button (actually a shifted button) that lets you take any root you want without having to inverse it (but it takes the same number of key strokes either way...minimum of 5). It's just that the button is right there waiting to be used.
(Hey...we're all sick of the Mac vs. PC debate. Time to start an HP vs. TI war. )

 

[Denward]

How about take the log of the number, dividing it by 3, and then hitting 10^x.
I believe that the easiest method is not the one with the least keystrokes, but the one that's most intuitive and repeatable for you.
BTW, I'm an HP man but I use their business calculators. I used to use the 12C but now I really like my 17BII.

 

[Scott Burke]

Thanks for the replies guys! I never thought of doing it that way. I just assumed that because my trusty TI 85 had a button for it so would the 89. However, I realize that is not the case. Thanks!