1*48919Scael.\" Copyright (c) 1991 The Regents of the University of California. 2*48919Scael.\" All rights reserved. 3*48919Scael.\" 4*48919Scael.\" %sccs.include.redist.man% 5*48919Scael.\" 6*48919Scael.\" @(#)atan.3 5.1 (Berkeley) 05/02/91 7*48919Scael.\" 8*48919Scael.Dd 9*48919Scael.Dt ATAN 3 10*48919Scael.Os 11*48919Scael.Sh NAME 12*48919Scael.Nm atan 13*48919Scael.Nd arc tangent function of one variable 14*48919Scael.Sh SYNOPSIS 15*48919Scael.Fd #include <math.h> 16*48919Scael.Ft double 17*48919Scael.Fn atan "double x" 18*48919Scael.Sh DESCRIPTION 19*48919ScaelThe 20*48919Scael.Fn atan 21*48919Scaelfunction computes the principal value of the arc tangent of 22*48919Scael.Fa x . 23*48919ScaelFor a discussion of error due to roundoff, see 24*48919Scael.Xr math 3 . 25*48919Scael.Sh RETURN VALUES 26*48919ScaelThe 27*48919Scael.Fn atan 28*48919Scaelfunction returns the arc tangent in the range 29*48919Scael.Bk -words 30*48919Scael.Bq -\*(Pi/2 , +\*(Pi/2 31*48919Scael.Ek 32*48919Scaelradians. 33*48919Scael.Sh SEE ALSO 34*48919Scael.Xr acos 3 , 35*48919Scael.Xr asin 3 , 36*48919Scael.Xr atan2 3 , 37*48919Scael.Xr cos 3 , 38*48919Scael.Xr cosh 3 , 39*48919Scael.Xr sin 3 , 40*48919Scael.Xr sinh 3 , 41*48919Scael.Xr tan 3 , 42*48919Scael.Xr tanh 3 , 43*48919Scael.Xr math 3 , 44*48919Scael.Sh STANDARDS 45*48919ScaelThe 46*48919Scael.Fn atan 47*48919Scaelfunction conforms to 48*48919Scael.St -ansiC . 49