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fea681da | 1 | .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk) |
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2 | .\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk |
3 | .\" <mtk.manpages@gmail.com> | |
fea681da | 4 | .\" |
93015253 | 5 | .\" %%%LICENSE_START(VERBATIM) |
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6 | .\" Permission is granted to make and distribute verbatim copies of this |
7 | .\" manual provided the copyright notice and this permission notice are | |
8 | .\" preserved on all copies. | |
9 | .\" | |
10 | .\" Permission is granted to copy and distribute modified versions of this | |
11 | .\" manual under the conditions for verbatim copying, provided that the | |
12 | .\" entire resulting derived work is distributed under the terms of a | |
13 | .\" permission notice identical to this one. | |
c13182ef | 14 | .\" |
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15 | .\" Since the Linux kernel and libraries are constantly changing, this |
16 | .\" manual page may be incorrect or out-of-date. The author(s) assume no | |
17 | .\" responsibility for errors or omissions, or for damages resulting from | |
18 | .\" the use of the information contained herein. The author(s) may not | |
19 | .\" have taken the same level of care in the production of this manual, | |
20 | .\" which is licensed free of charge, as they might when working | |
21 | .\" professionally. | |
c13182ef | 22 | .\" |
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23 | .\" Formatted or processed versions of this manual, if unaccompanied by |
24 | .\" the source, must acknowledge the copyright and authors of this work. | |
4b72fb64 | 25 | .\" %%%LICENSE_END |
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26 | .\" |
27 | .\" References consulted: | |
28 | .\" Linux libc source code | |
29 | .\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991) | |
30 | .\" 386BSD man pages | |
31 | .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu) | |
32 | .\" Modified 2002-07-27 by Walter Harms | |
33 | .\" (walter.harms@informatik.uni-oldenburg.de) | |
34 | .\" | |
fe0fefbf | 35 | .TH ATAN2 3 2015-03-02 "" "Linux Programmer's Manual" |
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36 | .SH NAME |
37 | atan2, atan2f, atan2l \- arc tangent function of two variables | |
38 | .SH SYNOPSIS | |
39 | .nf | |
40 | .B #include <math.h> | |
1cdac39d | 41 | |
fea681da | 42 | .BI "double atan2(double " y ", double " x ); |
fea681da | 43 | .BI "float atan2f(float " y ", float " x ); |
fea681da | 44 | .BI "long double atan2l(long double " y ", long double " x ); |
1cdac39d | 45 | |
fea681da | 46 | .fi |
20c58d70 | 47 | Link with \fI\-lm\fP. |
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48 | .sp |
49 | .in -4n | |
50 | Feature Test Macro Requirements for glibc (see | |
51 | .BR feature_test_macros (7)): | |
52 | .in | |
53 | .sp | |
54 | .ad l | |
55 | .BR atan2f (), | |
56 | .BR atan2l (): | |
fd39aa34 | 57 | .RS |
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58 | _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE || |
59 | _POSIX_C_SOURCE\ >=\ 200112L; | |
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60 | .br |
61 | or | |
f71288ac | 62 | .I cc\ -std=c99 |
fd39aa34 | 63 | .RE |
f71288ac | 64 | .ad b |
fea681da | 65 | .SH DESCRIPTION |
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66 | The |
67 | .BR atan2 () | |
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68 | function calculates the principal value of the arc tangent of |
69 | .IR y/x , | |
70 | using the signs of the two arguments to determine | |
71 | the quadrant of the result. | |
47297adb | 72 | .SH RETURN VALUE |
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73 | On success, these functions return the principal value of the arc tangent of |
74 | .IR y/x | |
d62d92dc | 75 | in radians; the return value is in the range [\-pi,\ pi]. |
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76 | |
77 | If | |
78 | .I y | |
79 | is +0 (\-0) and | |
80 | .I x | |
81 | is less than 0, +pi (\-pi) is returned. | |
82 | ||
83 | If | |
84 | .I y | |
85 | is +0 (\-0) and | |
86 | .I x | |
87 | is greater than 0, +0 (\-0) is returned. | |
88 | ||
89 | If | |
90 | .I y | |
91 | is less than 0 and | |
92 | .I x | |
93 | is +0 or \-0, \-pi/2 is returned. | |
94 | ||
95 | If | |
96 | .I y | |
97 | is greater than 0 and | |
98 | .I x | |
99 | is +0 or \-0, pi/2 is returned. | |
100 | ||
101 | .\" POSIX.1 says: | |
102 | .\" If | |
103 | .\" .I x | |
104 | .\" is 0, a pole error shall not occur. | |
105 | .\" | |
106 | If either | |
107 | .I x | |
108 | or | |
109 | .I y | |
110 | is NaN, a NaN is returned. | |
111 | ||
112 | .\" POSIX.1 says: | |
4e836144 | 113 | .\" If the result underflows, a range error may occur and |
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114 | .\" .I y/x |
115 | .\" should be returned. | |
116 | .\" | |
117 | If | |
118 | .I y | |
119 | is +0 (\-0) and | |
120 | .I x | |
121 | is \-0, +pi (\-pi) is returned. | |
122 | ||
123 | If | |
124 | .I y | |
125 | is +0 (\-0) and | |
126 | .I x | |
127 | is +0, +0 (\-0) is returned. | |
128 | ||
129 | If | |
130 | .I y | |
131 | is a finite value greater (less) than 0, and | |
132 | .I x | |
133 | is negative infinity, +pi (\-pi) is returned. | |
134 | ||
135 | If | |
136 | .I y | |
137 | is a finite value greater (less) than 0, and | |
138 | .I x | |
139 | is positive infinity, +0 (\-0) is returned. | |
140 | ||
141 | If | |
142 | .I y | |
143 | is positive infinity (negative infinity), and | |
144 | .I x | |
145 | is finite, | |
146 | pi/2 (\-pi/2) is returned. | |
147 | ||
148 | If | |
149 | .I y | |
150 | is positive infinity (negative infinity) and | |
151 | .I x | |
c3074d70 | 152 | is negative infinity, +3*pi/4 (\-3*pi/4) is returned. |
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153 | |
154 | If | |
155 | .I y | |
156 | is positive infinity (negative infinity) and | |
157 | .I x | |
c3074d70 | 158 | is positive infinity, +pi/4 (\-pi/4) is returned. |
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159 | .\" |
160 | .\" POSIX.1 says: | |
161 | .\" If both arguments are 0, a domain error shall not occur. | |
162 | .SH ERRORS | |
163 | No errors occur. | |
164 | .\" POSIX.1 documents an optional underflow error | |
165 | .\" glibc 2.8 does not do this. | |
54e5aeaa MS |
166 | .SH ATTRIBUTES |
167 | For an explanation of the terms used in this section, see | |
168 | .BR attributes (7). | |
169 | .TS | |
170 | allbox; | |
171 | lbw28 lb lb | |
172 | l l l. | |
173 | Interface Attribute Value | |
174 | T{ | |
175 | .BR atan2 (), | |
176 | .BR atan2f (), | |
177 | .BR atan2l () | |
178 | T} Thread safety MT-Safe | |
179 | .TE | |
47297adb | 180 | .SH CONFORMING TO |
9a74e018 | 181 | C99, POSIX.1-2001, POSIX.1-2008. |
e05e3635 | 182 | |
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183 | The variant returning |
184 | .I double | |
185 | also conforms to | |
f71288ac | 186 | SVr4, 4.3BSD, C89. |
47297adb | 187 | .SH SEE ALSO |
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188 | .BR acos (3), |
189 | .BR asin (3), | |
190 | .BR atan (3), | |
a1759255 | 191 | .BR carg (3), |
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192 | .BR cos (3), |
193 | .BR sin (3), | |
194 | .BR tan (3) |