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1.\" Stephen Canon, Apple Inc
2.Dd July 6, 2010
3.Dt M_PI 3
4.Os
5.Sh NAME
6.Nm constants
7.Nd mathematical library constants
8.Sh SYNOPSIS
9.Fd #include <math.h>
10.Sh DESCRIPTION
11The header file math.h provides macros that define a number of useful numerical
12constants.
13.Sh LIST OF CONSTANTS
14As required by the POSIX standard, these constants are double-precision literals,
15with enough digits specified as to ensure that they are correctly rounded in
16double-precision:
17.Pp
18.Dv M_E
19.Pp
20"Euler's constant" or e; the base of the natural logarithm.
21.Pp
22.Dv M_LOG2E
23.br
24.Dv M_LOG10E
25.Pp
26The logarithms of e in base 2 and 10, respectively.
27.Pp
28.Dv M_LN2
29.br
30.Dv M_LN10
31.Pp
32The natural logarithms of 2 and 10, respectively. Note that these are the
33reciprocals of the preceeding two values.
34.Pp
35.Dv M_PI
36.br
37.Dv M_PI_2
38.br
39.Dv M_PI_4
40.Pp
41pi, pi/2, and pi/4, respectively.
42.Pp
43.Dv M_1_PI
44.br
45.Dv M_2_PI
46.Pp
471/pi and 2/pi, respectively.
48.Pp
49.Dv M_2_SQRTPI
50.Pp
51Two divided by the square root of pi.
52.Pp
53.Dv M_SQRT2
54.br
55.Dv M_SQRT_1_2
56.Pp
57The square root of two and its reciprocal, respectively.
58.Sh SEE ALSO
59.Xr math 3 ,
60.Xr float 3 ,
61.Sh STANDARDS
62The <math.h> functions and macros conform to the ISO/IEC 9899:1999(E) standard.