acos(x [, degrees:T or radians:T or cycles:T]), x REAL or a structure with REAL components value in radians (default), cycles, or degrees as specified by option "angles" or the optional keyword |

acos(x) computes the inverse cosines of the elements of x, where x is a REAL scalar, vector, matrix or array. The result has the same shape as x. cos(acos(x)) should be the same as x except for rounding error. The units of the result are radians, degrees or cycles as determined by the value of option 'angles'. The default is radians. See subtopic 'options:"angles"'. acos(x, radians:T), acos(x, degrees:T), acos(x, cycles:T) return results in the indicated units, regardless of the value of option 'angles'. When any element of x is MISSING or is above 1 or below -1, the corresponding element of the result is MISSING and a warning message is printed. When x is a structure, all of whose non-structure components are REAL, acos(x [,UNITS:T]), where UNITS is one of 'radians', 'degrees' or 'cycles', is a structure of the same shape and with the same component names as x with each non-structure component transformed by acos(). Cmd> vector(acos(.5),acos(.5,degrees:T),acos(.5,cycles:T)) (1) 1.0472 60 0.16667 See topic 'transformations' for more information on acos(), including its use with a CHARACTER argument.

Gary Oehlert 2003-01-15