Request to provide some reference on sin/cos calculation algorithms used in slaa518a app. note

Dear TI Experts,

In the fixed point version of code example for slaa518a app.note:

Nine-Axis Sensor Fusion Using the Direction Cosine
Matrix Algorithm on the MSP430F5xx Family

There is a function called my_sin_cos which calculates sin and cos for a given angle.

Could you please let me know some reference where the calculation algorithm is described.

The code snippet is below:

Regards,

Artak

void my_sin_cos(int16_t A, int16_t *s, int16_t *c)
{
  // input = radians in Q4.12
  // ouput in Q4.12
    int16_t Y,X,i,dx,dy,da,s_sgn, c_sgn, Y1, X1;
    //const int16_t LUT[13] = {3217, 1899, 1003, 509, 256, 128, 64, 32, 16, 8, 4, 2, 1}; //Q4.12
        
        
        // check if A is > pi or <-pi
        if (A >= 0x3244) // pi in Q4.12
        {
          A = A-0x6488; // 2*pi in Q4.12
        }
        else if (A <= -0x3244)
        {
          A = A + 0x6488;
        }
        
        /*** at this point -pi <= A <= pi ***/

    Y=0;
    X=0x09b7; // stg:0.60725 in Q4.12
        
        s_sgn=0;
        c_sgn=0;
        if (A < 0)
        {
          A=-A;
          s_sgn=1;
        }
        
        /*** at this point 0 <= A <= pi ***/

        if (A > 0x1922 ) // pi/2 in Q4.12
        {
          A = 0x3244-A;  // pi - A
          c_sgn=1;
        }
        
        /*** at this point 0 <= A <= pi/2 ***/
        Y1=Y;
        X1=X;

    for(i=0;i<8;i++)
    {            
                        
        dx=(X1>>i);
        dy=(Y1>>i);
        da=_AngLUT[i];

        if (A>=0)
        {
            X=X-dy;
            Y=Y+dx;
            A=A-da;
        }
        else
        {
            X=X+dy;
            Y=Y-dx;
            A=A+da;
        }
                
                Y1=Y;
        X1=X;
        
        if (X<0) // logic to take care of neg div in fixed
        {
            if (-X < 0x0001<<i+1)
                {X1=0;}
            else
                {X1+=(0x0001<<i);}
        }
        
        if (Y<0)
        {
            if (-Y < 0x0001<<i+1)
                {Y1=0;}
            else
                {Y1+=(0x0001<<i);}
        }
    }
        
        if (s_sgn==1)
          Y=-Y;
        if (c_sgn==1)
          X=-X;
        
    *s=Y; //(Q4.12)
    *c=X;
}