coordinate angle size without π

First, according to x and x axis angle, tanx=y/x;

ATAN2 usage: atan2 (Y,X) is expressed in the sense that the origin of the coordinates is the starting point, and the angle of the (x, y) ray on the coordinate plane and the positive direction of the x-axis. The code shows the following columns:

1   while(n--)2     {3scanf"%LF%LF%LF%LF",&x1,&y1,&x2,&y2);4a1=atan2 (y1,x1);5A2=atan2 (y2,x2);6A3=fabs (a1-A2);7printf"%.2lf\n", a3* the/PI);8}

Second, according to the angle of x, cosx= vector a point multiplication vector b/Mode A *

 while (n--)    {        double  x1,x2,y1,y2,t,a,b,c;        scanf ("%lf%lf%lf%lf",&x1,&y1,&x2,&y2);        A=x1*x2+y1*y2;        b=sqrt (x2*x2+y2*y2);        C=sqrt (x1*x1+y1*y1);        T=acos (A/B/C) *N/PI;        printf ("%.2lf\n", T);    }

coordinate angle size without π