B101: Arc Tangent Function

Author(s): K.S. Kölbig	Library: MATHLIB
Submitter:	Submitted: 15.02.1989
Language: Fortran	Revised: 15.03.1993

Function subprogram ATG calculates, for real arguments and , , an angle such that

Note that using the Fortran intrinsic function ATAN2 instead of ATG would result in

Structure:

FUNCTION subprogram

User Entry Names: ATG

Usage:

In any arithmetic expression,

ATG(X1,X2)

has the value of (in radians). ATG, X1 and X2 are of type REAL.

Notes:

This function subprogram is equivalent to the statement function

ATG(X1,X2)=ATAN2(X1,X2)+(PI-SIGN(PI,X1))

where .