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    computing roots on a calculator

    currently calculators accept square roots as sqrt(9) which is 3

    but how to change the root so as to compute a cube root or more than 3rd roots?

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    Re: computing roots on a calculator

    A basic method to take cube root of 9:
    * take log(9)
    * divide by 3
    * take antilog

    A scientific calculator has a button to calculate X to the Y power. The cube root of 9= (9)^1/3 power.

    Or a button to calculate #Xth root of Y.


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    Re: computing roots on a calculator

    Quote Originally Posted by BradtheRad View Post
    A basic method to take cube root of 9:
    * take log(9)
    * divide by 3
    * take antilog

    A scientific calculator has a button to calculate X to the Y power. The cube root of 9= (9)^1/3 power.

    Or a button to calculate #Xth root of Y.
    I meant on calculators such as bc or the google chrome searchbar calculator.



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    Re: computing roots on a calculator

    It cannot be done (in a single step) on a basic calculator; but the search bar calculator is quite powerful.

    You can type either ** or a ^ as the power symbol (operation). In other words, x**y and x^y means the same: x raised to the power of y.

    If the power is integer you simply type it as such. For roots (say cube roots) you need to type 1/3 in parenthesis: 27^(1/3) will give you 3.

    Internally, the numeric processor uses an algorithm very similar to the one pointed out in post #2. If both x and y are floats, x^y is computationally very expensive in time (it does take lots of time or cpu cycles).


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    Re: computing roots on a calculator

    They should implement

    crt(x) cube root
    qrt(x) quad root

    currently only sqrt(x) is implemented.



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    Re: computing roots on a calculator

    The nth root of a number x can be found by x^(1/n). If you have the x-power-time button, then you use it.

    - - - Updated - - -

    Quote Originally Posted by Zak28 View Post
    They should implement

    crt(x) cube root
    qrt(x) quad root

    currently only sqrt(x) is implemented.
    It has already been implemented. But it's dynamic, so you can select the power you wish yourself. That is what has been done with the x^y function.
    -------------
    --Akanimo.


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    Re: computing roots on a calculator

    qrt(x) quad root
    It is simple if you have the sqrt function: quad root is nothing but sqrt(sqrt(x)).

    If you are familiar with Newton Raphson method, you can use that for many different problems.

    The real problems are (float)^(float)- they are hard to manage numerically.


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  8. #8
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    Re: computing roots on a calculator

    Quote Originally Posted by Akanimo View Post
    The nth root of a number x can be found by x^(1/n). If you have the x-power-time button, then you use it.

    - - - Updated - - -



    It has already been implemented. But it's dynamic, so you can select the power you wish yourself. That is what has been done with the x^y function.

    Its not implemented I might file a bug with bc if they have a tracker.



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    Re: computing roots on a calculator

    As documented, bc ^ operator supports only integer power arguments. e(l(x)/3) however works. You can define it as a function if you like. Or use a somewhat more elaborated calculator.


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