Manual Reference Pages  - acos (3fortran)

NAME

ACOS(3) - [MATHEMATICS:TRIGONOMETRIC] Arccosine (inverse cosine) function

SYNOPSIS

result = acos(x) 

         elemental TYPE(kind=KIND) function acos(x)


          TYPE(kind=KIND),intent(in) :: x

CHARACTERISTICS

o TYPE may be real or complex
o KIND may be any kind supported by the associated type.
o The returned value will be of the same type and kind as the argument.

DESCRIPTION

ACOS(3) computes the arccosine of X (inverse of COS(X)).

OPTIONS

o X : The value to compute the arctangent of. : If the type is real, the value must satisfy |X| <= 1.

RESULT

The return value is of the same type and kind as X. The real part of the result is in radians and lies in the range 0 <= ACOS(X%RE) <= PI .

EXAMPLES

Sample program: 

    program demo_acos
    use, intrinsic :: iso_fortran_env, only : real_kinds,real32,real64,real128
    implicit none
    character(len=*),parameter :: all=’(*(g0,1x))’
    real(kind=real64) :: x , d2r


       ! basics
        x = 0.866_real64
        print all,’acos(’,x,’) is ’, acos(x)


       ! acos(-1) should be PI
        print all,’for reference &
        &PI ~= 3.14159265358979323846264338327950288419716939937510’
        write(*,*) acos(-1.0_real64)
        d2r=acos(-1.0_real64)/180.0_real64
        print all,’90 degrees is ’, d2r*90.0_real64, ’ radians’
       ! elemental
        print all,’elemental’,acos([-1.0,-0.5,0.0,0.50,1.0])
       ! complex
        print *,’complex’,acos( (-1.0,  0.0) )
        print *,’complex’,acos( (-1.0, -1.0) )
        print *,’complex’,acos( ( 0.0, -0.0) )
        print *,’complex’,acos( ( 1.0,  0.0) )


    end program demo_acos
Results: 

     acos( 0.86599999999999999 ) is  0.52364958093182890
     for reference PI ~= 3.14159265358979323846264338327950288419716939937510
        3.1415926535897931
     90 degrees is  1.5707963267948966  radians
     elemental 3.14159274 2.09439516 1.57079637 1.04719758 0.00000000
      complex            (3.14159274,-0.00000000)
      complex             (2.23703575,1.06127501)
      complex             (1.57079637,0.00000000)
      complex            (0.00000000,-0.00000000)

STANDARD

FORTRAN 77 ; for a complex argument - Fortran 2008

SEE ALSO

Inverse function: COS(3)

RESOURCES

o wikipedia: inverse trigonometric functions
fortran-lang intrinsic descriptions (license: MIT) @urbanjost

Nemo Release 3.1 acos (3fortran) April 28, 2024
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