tanf
extern float tanf(float x);
float c_value = (1 - tanf(theta * q / 2.0)) / (1 + tanf(theta * q / 2.0));
t[2] = tanf(a); t[3] = 1.0f;
t[0] = 1.0f; t[1] = tanf(a);
t = tanf(y);