Math Constants 사용하기

출처: MSDN

---

The following symbols are defined for the values of their indicated expressions:

Symbol	Expression	Value
M_E	e	2.71828182845904523536
M_LOG2E	log2(e)	1.44269504088896340736
M_LOG10E	log10(e)	0.434294481903251827651
M_LN2	ln(2)	0.693147180559945309417
M_LN10	ln(10)	2.30258509299404568402
M_PI	pi	3.14159265358979323846
M_PI_2	pi/2	1.57079632679489661923
M_PI_4	pi/4	0.785398163397448309616
M_1_PI	1/pi	0.318309886183790671538
M_2_PI	2/pi	0.636619772367581343076
M_2_SQRTPI	2/sqrt(pi)	1.12837916709551257390
M_SQRT2	sqrt(2)	1.41421356237309504880
M_SQRT1_2	1/sqrt(2)	0.707106781186547524401

The "Math Constants" are not defined in Standard C/C++. Therefore, in order to use them, you have to first define _USE_MATH_DEFINES and then include cmath or math.h as below.


If compiling as C++:

#define _USE_MATH_DEFINES

#include <cmath>


If compiling as C:

#define _USE_MATH_DEFINES

#include <math.h>

---

Visual Studio 2008 기준으로 프로그램에서 수학 상수들을 사용하기 위해서는

위와 같이 math.h 또는 cmath를 include하여야 하며,

이때 include 이전에 "#define _USE_MATH_DEFINES" 를 먼저 선언해 주어야 한다.