# wcsmath.h File Reference

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## Defines
#define | PI 3.141592653589793238462643
#define | D2R PI/180.0
| Degrees to radians conversion factor.
#define | R2D 180.0/PI
| Radians to degrees conversion factor.
#define | SQRT2 1.4142135623730950488
#define | SQRT2INV 1.0/SQRT2
#define | UNDEFINED 987654321.0e99
| Value used to indicate an undefined quantity.
#define | undefined(value) (value == UNDEFINED)
| Macro used to test for an undefined quantity.

## Detailed Description

Definition of mathematical constants used by WCSLIB.

## Define Documentation

#define PI 3.141592653589793238462643

#define D2R PI/180.0

Factor to convert from degrees to radians.

#define R2D 180.0/PI

Factor to convert from radians to degrees.

#define SQRT2 1.4142135623730950488

, used only by molset() (`MOL` projection).

#define SQRT2INV 1.0/SQRT2

, used only by qscx2s() (`QSC` projection).

#define UNDEFINED 987654321.0e99

Value used to indicate an undefined quantity (noting that NaNs cannot be used portably).

#define undefined | ( | value |  | ) | (value == UNDEFINED)

Macro used to test for an undefined value.