Lahey/GNU Fortran

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8.21 ATAN — Arctangent function

Description:
ATAN(X) computes the arctangent of X.
Standard:
Fortran 77 and later, for a complex argument and for two arguments Fortran 2008 or later
Class:
Elemental function
Syntax:

RESULT = ATAN(X)
RESULT = ATAN(Y, X)

Arguments:

X The type shall be REAL or COMPLEX; if Y is present, X shall be REAL.
Y shall be of the same type and kind as X.

Return value:
The return value is of the same type and kind as X. If Y is present, the result is identical to ATAN2(Y,X). Otherwise, it the arcus tangent of X, where the real part of the result is in radians and lies in the range -\pi/2 \leq \Re \atan(x) \leq \pi/2.
Example:
          program test_atan
            real(8) :: x = 2.866_8
            x = atan(x)
          end program test_atan
     

Specific names:

Name Argument Return type Standard
ATAN(X) REAL(4) X REAL(4) Fortran 77 and later
DATAN(X) REAL(8) X REAL(8) Fortran 77 and later

See also:
Inverse function: TAN