I am trying to use the nth root for natural numbers in computations and display the result as a decimal to four places. I can't find a simple reference for these functions. Is there an nroot(x,n) function?
Usually this comes up in plotting. See the Sage reference and search the page for "cube root".
sage: a = 2
sage: b = a.n()
sage: b
2.00000000000000
sage: b.nth_root(3)
1.25992104989487
sage: _^3 # _ means the previous output
2.00000000000000There is an nth_root for real numbers like this, but be careful if you want to try this for plain old integers:
sage: a.nth_root(3)
---------------------------------------------------------------------------
<snip>
ValueError: 2 is not a 3rd power"# _ means the previous input" or output? equivalent to "ans" in MATLAB. And we can use a.nth_root(3, truncate_mode = 1). --> (1, False).
Yes, output of course - I'll edit that.
I don't think there is one but you can define one using a couple of lines of code
def nroot(x,n):
return x**(1/n).n()
nroot(8,3)Not so easy when you try def nroot(x,n): return x**(1/n).n() nroot(-8,3) You don't get the real root- but instead: 1.00000000000000 + 1.73205080756888*I There's the rub. :(
It is supposed to be complex. You cannot have real cube root for -8.
You can't? I always thought -2 cubed was -8 ... :-) But it is true that Sage returns a sort of "primitive nth root" (whatever that means) by default.
Sorry about that.
Asked: 11 years ago
Seen: 13,168 times
Last updated: Nov 13 '13
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