Name | Synopsis | Description | Return Values | Errors | Attributes | See Also

- atan2, atan2f, atan2l– arc tangent function

c99 [flag... ]file...[-lmlibrary... ] #include <math.h>doubleatan2(doubley,doublex);

floatatan2f(floaty,floatx);

long doubleatan2l(long doubley,long doublex);

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.

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

If `y` is ±0 and `x` is < 0, ±π is returned.

If `y` is ±0 and `x` is > 0, ±0 is returned.

If `y` is < 0 and `x` is ±0, -π/2 is returned.

If `y` is > 0 and `x` is ±0, π/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, ±π is returned.

If `y` is ±0 and `x` is +0, ±0 is returned.

For finite values of ±`y` > 0, if x is -Inf, ±π is returned.

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

For finite values of `x`, if `y` is ±Inf, ±π/2 is returned.

If `y` is ±Inf and `x` is -Inf, ±3π/4 is returned.

If `y` is ±Inf and `x` is +Inf, ±π/4 is returned.

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

No errors are defined.

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

ATTRIBUTE TYPE |
ATTRIBUTE VALUE |
---|---|

Interface Stability |
Standard |

MT-Level |
MT-Safe |

Name | Synopsis | Description | Return Values | Errors | Attributes | See Also

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