I have a file where I defined all my constants. Why can't i use trig Identities in this files

#include <math.h>

//Define constants

#define gamma 1.4

#define Pr 0.71

#define mu_ref 1.7894e-5 // kg/(m*s)

#define T_ref 288.16 // K

#define R_gas 287

#define incidence 11

#define P1 0.714 // N/(m^2)

#define P2 P1*2.153 // N/(m^2)

#define rho1 1.225 // kg/(m^3)

#define rho2 rho1*1.707 // kg/(m^3)

#define Mach 2.9 // m/s

#define u1 sqrt(gamma*R_gas*T_ref) //m/s

#define u2 u1*1.707*sin(incidence) m/s */

#define u_ratio sqrt(1.707)

#define Theta atan(u_ratio) - atan(1/u_ratio)

#define v1 0 // m/s

#define v2 u2*sin(Theta) // m/s