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ATAN2 3M "Jul 12, 2006" "SunOS 5.11" "Mathematical Library Functions"
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 [ -\c \c ,\c \c ] radians.

If y is \(+-0 and x is < 0, \(+-\c \c is returned.

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

If y is < 0 and x is \(+-0, -\c \c /2 is returned.

If y is > 0 and x is \(+-0, \c \c /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, \(+-\c \c is returned.

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

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

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

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

If y is \(+-Inf and x is -Inf, \(+-3\c \c /4 is returned.

If y is \(+-Inf and x is +Inf, \(+-\c \c /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