.\" Copyright (c) 1991 The Regents of the University of California. | |

.\" All rights reserved. | |

.\" | |

.\" Redistribution and use in source and binary forms, with or without | |

.\" modification, are permitted provided that the following conditions | |

.\" are met: | |

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.\" notice, this list of conditions and the following disclaimer. | |

.\" 2. Redistributions in binary form must reproduce the above copyright | |

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.\" 3. All advertising materials mentioning features or use of this software | |

.\" must display the following acknowledgement: | |

.\" This product includes software developed by the University of | |

.\" California, Berkeley and its contributors. | |

.\" 4. Neither the name of the University nor the names of its contributors | |

.\" may be used to endorse or promote products derived from this software | |

.\" without specific prior written permission. | |

.\" | |

.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND | |

.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |

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.\" | |

.\" from: @(#)acos.3 5.1 (Berkeley) 5/2/91 | |

.\" $FreeBSD: src/lib/msun/man/acos.3,v 1.13 2005/01/14 23:28:28 das Exp $ | |

.\" | |

.Dd January 14, 2005 | |

.Dt ACOS 3 | |

.Os | |

.Sh NAME | |

.Nm acos , | |

.Nm acosf | |

.Nd arc cosine functions | |

.Sh LIBRARY | |

.Lb libm | |

.Sh SYNOPSIS | |

.In math.h | |

.Ft double | |

.Fn acos "double x" | |

.Ft float | |

.Fn acosf "float x" | |

.Sh DESCRIPTION | |

The | |

.Fn acos | |

and the | |

.Fn acosf | |

functions compute the principal value of the arc cosine of | |

.Fa x . | |

A domain error occurs for arguments not in the range | |

.Bq -1 , +1 . | |

For a discussion of error due to roundoff, see | |

.Xr math 3 . | |

.Sh RETURN VALUES | |

The | |

.Fn acos | |

and the | |

.Fn acosf | |

functions return the arc cosine in the range | |

.Bq 0 , \*(Pi | |

radians. | |

If: | |

.Bd -unfilled -offset indent | |

.Pf \&| Ns Ar x Ns \&| > 1 , | |

.Ed | |

.Pp | |

.Fn acos x | |

raises an invalid exception and returns an \*(Na. | |

.Sh SEE ALSO | |

.Xr asin 3 , | |

.Xr atan 3 , | |

.Xr atan2 3 , | |

.Xr cos 3 , | |

.Xr cosh 3 , | |

.Xr fenv 3 , | |

.Xr math 3 , | |

.Xr sin 3 , | |

.Xr sinh 3 , | |

.Xr tan 3 , | |

.Xr tanh 3 | |

.Sh STANDARDS | |

The | |

.Fn acos | |

function conforms to | |

.St -isoC . |