var pi = 3.14159265358979;  //pi to 15sf
   function degToRad(x) { return ( x/(360/(2*pi)) ); }
   function radToDeg(x) { return ( x*(360/(2*pi)) ); }
  
   function matrixMultiply(A,B) {
    var retVal = [0,0,0];
    for(var m=0;m<4;m++) {
     for(var n=0;n<4;n++)
      retVal[m] += A[n] * B[m][n]
    }
    return retVal;
   }
   
  </script>