acosm matrix wise cosine inverse

## Syntax

    t = acosm(x)

## Arguments

x

  a real or complex square matrix.

t

  a real or complex square matrix.

## Description

`t` are cosine inverse of the `x` matrix. Diagonalization method is used. For non-symmetric matrices result may be inaccurate. One has `t=-%i*logm(x+%i*sqrtm(eye()-x*x))`.

## Examples

    A=[1,2;3,4];
    cosm(acosm(A))

## See also

- acos
- sqrtm
- logm