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ATAN — Arctangent functionATAN(X) computes the arctangent of X.
Fortran 77 and later, for a complex argument and for two arguments Fortran 2008 or later
Elemental function
| RESULT = ATAN(X) | 
| RESULT = ATAN(Y, X) | 
| X | The type shall be REALorCOMPLEX;
if Y is present, X shall be REAL. | 
| Y shall be of the same type and kind as X. | 
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.
program test_atan real(8) :: x = 2.866_8 x = atan(x) end program test_atan
| 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 | 
Inverse function: TAN