I want to use the PI constant and trigonometric functions in some C++ program. I get the trigonometric functions with
include <math.h>. However, there doesn’t seem to be a definition for PI in this header file.
How can I get PI without defining it manually?
On some (especially older) platforms (see the comments below) you might need to
and then include the necessary header file:
and the value of pi can be accessed via:
math.h (2014) it is defined as:
# define M_PI 3.14159265358979323846 /* pi */
but check your
math.h for more. An extract from the “old”
math.h (in 2009):
/* Define _USE_MATH_DEFINES before including math.h to expose these macro * definitions for common math constants. These are placed under an #ifdef * since these commonly-defined names are not part of the C/C++ standards. */
on newer platforms (at least on my 64 bit Ubuntu 14.04) I do not need to define the
On (recent) Linux platforms there are
long doublevalues too provided as a GNU Extension:
# define M_PIl 3.141592653589793238462643383279502884L /* pi */