Copyright © 1997 The Open Group

atan - arc tangent function

`#include <math.h> double atan(double`

x);

Theatan()function computes the principal value of the arc tangent ofx.An application wishing to check for error situations should set

errnoto 0 before callingatan(). Iferrnois non-zero on return, or the return value is NaN, an error has occurred.

Upon successful completion,atan()returns the arc tangent ofxin the range [-/2, /2] radians.If

xis NaN, NaN is returned anderrnomay be set to [EDOM].If the result underflows, 0.0 is returned and

errnomay be set to [ERANGE].

Theatan()function may fail if:

- [EDOM]
- The value of
xis NaN.- [ERANGE]
- The result underflows.
No other errors will occur.

None.

None.

None.

atan2(),isnan(),tan(),<math.h>.

Derived from Issue 1 of the SVID.

Copyright © 1997 The Open Group

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