This file contains declarations of all the functions in the Math Library (described in Section 3M), as well as various functions in the C Library (Section 3C) that return floatingpoint values.
It defines the structure and constants used by the matherr(3M)
errorhandling mechanisms, including the following constant used as a errorreturn value:

HUGE
 The maximum value of a singleprecision floatingpoint number.
The following mathematical constants are defined for user convenience:

M_E
 The base of natural logarithms (e).

M_LOG2E
 The base2 logarithm of e.

M_LOG10E
 The base10 logarithm of e.

M_LN2
 The natural logarithm of 2.

M_LN10
 The natural logarithm of 10.

M_PI

pi, the ratio of the circumference of a circle to its diameter.

M_PI_2

pi/2.

M_PI_4

pi/4.

M_1_PI
 1/pi.

M_2_PI
 2/pi.

M_2_SQRTPI
 2 over the square root of pi.

M_SQRT2
 The positive square root of 2.

M_SQRT1_2
 The positive square root of 1/2.
The following mathematical constants are also defined in this header file:

MAXFLOAT
 The maximum value of a noninfinite singleprecision floating point
number.

HUGE_VAL
 positive infinity. For the definitions of various machinedependent constants see values(3HEAD).
