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The root() Command

Command Summary Command Syntax Calculator Compatibility Token Size
Takes the nth root of a value. root(value,n) This command requires a TI-89 Titanium or Voyage 200 calculator with AMS version 3.10 or higher. 2 bytes
  • Press 2nd MATH to enter the MATH popup menu.
  • Press 1 to enter the Number submenu.
  • Press D to select root(.

The root() Command

The root() command takes nth roots: root(x,2) is the square root of x, root(x,3) is the cubic root, etc. (n doesn't have to be a whole number, or even real). Since root(x,n) is equivalent to x^(1/n), there was never any real need for this command, but it was added in the last AMS update for the Voyage 200 and TI-89 Titanium because users complained about not being able to do this calculation.

As far as complex roots are concerned: if taking a root of a real number, root() will return the real branch if there is one. If taking the root of a complex number, it will always return the principal branch.

:root(x,2)
           √(x)
:root(1024,10)
           2

Advanced Uses

The command uses the same routines as the ^ operator, so it works in all the same ways. This means it can be applied to lists (element-wise), and to matrices either through repeated multiplication (e.g. if taking the 1/100th root of a matrix, which ends up being its 100th power) or by diagonalizing the matrix first (see 68k:matrices for mor information about this method). If you want to take the nth root of every element of a matrix, use the .^ command.

Optimization

You can save a few bytes of space by using root(x,n) instead of x^(1/n); however, this optimization is a bit dodgy. It requires AMS 3.10 to use, so if you're planning on releasing the program anywhere, it will only work on the TI-89 Titanium and the Voyage 200, and even then it might require updating the OS. It's probably not worth it, unless the program is for personal use only.

Error Conditions

230 - Dimension happens when non-square matrices are used with root().
230 - Domain error happens when a matrix is raised to an integer power not in the range -32768..32767.
665 - Matrix not diagonalizable happens when diagonalization (used to compute most uses of root() with matrices) fails.
800 - Non-real result happens when there is no real result to return, and the calculator is in real number mode.
890 - Singular matrix happens when raising a matrix with no inverse to a negative power.

Authors: KG