Changing coordinate system using rotation 2D from canonical base UPDATE

Some weeks ago I wrote a C code for a particular case of changing coordinateas using rotation matrix and today I rewrote it for a general use:
CODE:

 1 #include<stdio.h>
 2  #include<math.h>
 3  #define PI 3.14159265
 4  double a[2][2],b[2],c[2],x;
 5  int i,j;
 6  /*initializare matrice rotatie*/
 7  void matrice_rotatie(double a[2][2],double x)
 8  {a[0][0]=a[1][1]=cos(x*2*PI/360);
 9  a[0][1]=-sin(x);
10  a[1][0]=sin(x);
11   }
12  /*rotatie*/
13  void rotatie(double b[2],double c[2],double a[2][2])
14  {
15       for(i=0;i<2;i++)
16                       for(j=0;j<2;j++)
17                                       c[i]+=a[i][j]*b[i];
18       }
19  /*afisare_matrice*/
20  void afis_matrice(double a[2][2]){
21        for (i = 0; i < 2; i++) {
22          for (j = 0; j < 2; j++)
23              printf("%.2lf ", a[i][j]);
24          printf("
");
25      }
26       }
27  int main(){
28  printf("Coordonatele punctului:");scanf("%lf %lf",&b[0],&b[1]);
29  printf("Unghiul de rotatie:");scanf("%lf",&x);
30  matrice_rotatie(a,x);
31  rotatie(b,c,a);
32  printf("coordonatele noi sunt:%.2lf  si %.2lf
",c[0],c[1]);
33  return 0;
34  }

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