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8.23 ASINPI — Circular arc sine function ¶

Description:

ASINPI(X) computes \asin(x) / \pi, which is a measure of an angle in half-revolutions.

Standard:

Fortran 2023

Class:

Elemental function

Syntax:

RESULT = ASINPI(X)

Arguments:

X	The type shall be REAL with -1 \leq x \leq 1.

Return value:

The return value has the same type and kind as X. It is expressed in half-revolutions and satisfies -0.5 \leq \asinpi (x) \leq 0.5.

Example:

program test_asinpi
  implicit none
  real, parameter :: x = 0.123, y(3) = [0.123, 0.45, 0.8]
  real, parameter :: a = asinpi(x), b(3) = asinpi(y)
  call foo(x, y)
contains
  subroutine foo(u, v)
    real, intent(in) :: u, v(:)
    real :: f, g(size(v))
    f = asinpi(u)
    g = asinpi(v)
    if (abs(a - f) > 8 * epsilon(f)) stop 1
    if (any(abs(g - b) > 8 * epsilon(f))) stop 2
  end subroutine foo
end program test_asinpi

See also:

ACOSPI — Circular arc cosine function
ATAN2PI — Circular arc tangent function
ATANPI — Circular arc tangent function