# ACOS()

Arcus cosine of the argument

Syntax

  ACOS (nCosine) -> nRadiant

Arguments

  <nCosine> the cosine of an angle

Returns

  <nRadiant> the angle whose cosine is <nCosine>

Description

  The function ACOS() is the inverse function of COS(). It takes a cosine value and returns the smallest(!) angle whose cosine equals to the argument. The return value is given in radiants (full angle equals 2*Pi - see DTOR() if you need to convert it into degress). Note, that <nCosine> must be between -1 and 1 and that <nRadiant> is always between 0 and PI().

Examples

          ? acos (0.0) --> PI()/2
          ? acos (0.5) --> 1.04719...
    Tests
          acos (0.0) == PI()/2
          acos (sqrt(1/2)) == PI()/4
          acos (1.0) == 0.0
          acos (-1.0) == PI()
          acos (0.0) == PI()/2  // and not -PI()/2, although cos (-PI()/2) == 0.0 !

Status

  Ready

Compliance

  ACOS() is compatible with CT3's ACOS().

Platforms

  All

Files

  Source is trig.c, library is libct.

See Also

- SIN()
- COS()
- TAN()
- COT()
- ASIN()
- ATAN()
- ATN2()
- SINH()
- COSH()
- TANH()
- RTOD()
- DTOR()
- PI()