The problem of using M_PI in VS and resolving angle to Radian & method of calculating the coordinates of points on the circumference by radians

M_PI is a macro definition, the definition of pi

C + + code

#define m_pi 3.14159265358979323846

This macro definition is related to the compiler, the M_PI macro in TC is defined in <math.h>.

But VC's <math.h> does not have the M_PI macro definition. As a result, there is an error at compile time, prompting: "M_pi": an undeclared identifier.

Workaround: Define by yourself.

Angle to radians:

#define Angletoradian (angle) (m_pi/180.0f) *angle

Calculates the coordinates of the points on the circumference of the specified angle at the positive east of the 0-degree start:

float Radian = Angletoradian (angle);

float x = center.x + cos (radian) *r;

Float y = center.y + sin (radian) *r;

Cgpoint point = Cgpointmake (x, y);

Calculates the coordinates of the points on the circumference of the specified angle at the beginning of the 0-degree point on the north side:

float Radian = Angletoradian (angle);

float x = center.x + sinf (radian) *r;

Float y = CENTER.Y-COSF (radian) *r;

Cgpoint point = Cgpointmake (x, y);

The problem of using M_PI in VS and resolving angle to Radian & method of calculating the coordinates of points on the circumference by radians