Manual Reference Pages  - atanpi (3fortran)

NAME

ATANPI(3) - [MATHEMATICS:TRIGONOMETRIC] Circular Arctangent AKA inverse tangent function

SYNOPSIS

result = atanpi([x) | atanpi(y, x) 

         elemental real(kind=KIND) function atanpi(y,x)


          real(kind=KIND),intent(in) :: x
          real(kind=KIND),intent(in),optional :: y

CHARACTERISTICS

o Y and X must both be real and of the same KIND
o KIND can be any kind supported by the real type.
o The returned value is of the same type and kind as X.

DESCRIPTION

ATAN(3) computes the circular arctangent of X in half-revolutions.

If Y appears, the result is the same as the result of ATAN2PI(Y,X). If Y does not appear, the result has a value equal to a processor-dependent approximation to the arc tangent of X; it is expressed in half-revolutions and lies in the range -0.5 <= ATANPI(X) <= 0.5.

Example. ATANPI(1.0) has the value 0.25 (approximately).

OPTIONS

o X : The real value to compute the arctangent of.
o Y : is of the same type and kind as X. If X is zero, Y must not be zero.

RESULT

The returned value is of the same type and kind as X. If Y is present, the result is identical to ATAN2PI(Y,X). Otherwise, it is the arc tangent of X, where the result is in half-revolutions and lies in the range -1 <= ATAN(X) <= 1

EXAMPLES

Sample program: 

    program demo_atanpi
    use, intrinsic :: iso_fortran_env, only : real32, real64
    implicit none
    character(len=*),parameter :: all=’(*(g0,1x))’
    real(kind=real64) :: x, y
        x=2.866_real64
        print all, atanpi(x)


        print all, atanpi( 2.0d0, 2.0d0),atanpi( 2.0d0, 2.0d0)*180
        print all, atanpi( 2.0d0,-2.0d0),atanpi( 2.0d0,-2.0d0)*180
        print all, atanpi(-2.0d0, 2.0d0),atanpi(-2.0d0, 2.0d0)*180
        print all, atanpi(-2.0d0,-2.0d0),atanpi(-2.0d0,-2.0d0)*180


    end program demo_atanpi
Results: 

     > 0.39313990502447488
     > 0.25000000000000000 45.000000000000000
     > 0.75000000000000000 135.00000000000000
     > -0.25000000000000000 -45.000000000000000
     > -0.75000000000000000 -135.00000000000000

STANDARD

Fortran 2023

SEE ALSO

ATAN2D(3), TAN2D(3), ATAN2PI(3), TAN2PI(3)

RESOURCES

o wikipedia: inverse trigonometric functions

Nemo Release 3.1 atanpi (3fortran) November 02, 2024
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