## Linux and UNIX Man Pages

Test Your Knowledge in Computers #239
Difficulty: Easy
In March 1970, the ARPANET reached the East Coast of the United States, when an IMP at the Department of Energy in Washington, DC was connected to the network.
True or False?

# atan2f(3m) [opensolaris man page]

```atan2(3M)						  Mathematical Library Functions						 atan2(3M)

NAME
atan2, atan2f, atan2l - arc tangent function

SYNOPSIS
c99 [ flag... ] file... -lm [ library... ]
#include <math.h>

double atan2(double y, double x);

float atan2f(float y, float x);

long double atan2l(long double y, long double x);

DESCRIPTION
These  functions  compute the principal value of the arc tangent of y/x, using the signs of both arguments to determine the quadrant of the
return value.

RETURN VALUES
Upon successful completion, these functions return the arc tangent of y/x in the range [ -pi,pi ] radians.

If y is +-0 and x is < 0, +-pi is returned.

If y is +-0 and x is > 0, +-0 is returned.

If y is < 0 and x is +-0, -pi/2 is returned.

If y is > 0 and x is +-0, pi/2 is returned.

If x is 0, a pole error does not occur.

If either x or y is NaN, a NaN is returned.

If y is +-0 and x is -0, +-pi is returned.

If y is +-0 and x is +0, +-0 is returned.

For finite values of +-y > 0, if x is -Inf,  +-pi is returned.

For finite values of +-y > 0, if x is +Inf,  +-0 is returned.

For finite values of x, if y is +-Inf, +-pi/2 is returned.

If y is +-Inf and x is -Inf, +-3pi/4 is returned.

If y is +-Inf and x is +Inf, +-pi/4 is returned.

If both arguments are 0, a domain error does not occur.

ERRORS
No errors are defined.

ATTRIBUTES
See attributes(5) for descriptions of the following attributes:

+-----------------------------+-----------------------------+
|      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
+-----------------------------+-----------------------------+
|Interface Stability	     |Standard			   |
+-----------------------------+-----------------------------+
|MT-Level		     |MT-Safe			   |
+-----------------------------+-----------------------------+