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#include "vector.h"
#include <math.h>
void normalize(double *a)
{
double c;
c = 1.0/NORM(a);
MUL(a,c);
}
void rotate(double *dest, double *v, double *n, double phi)
{
/* Rotate the vector `v` through an angle `phi` about the axis `n`. */
double temp[3], cos_theta;
cos_theta = cos(phi);
COPY(dest,v);
MUL(dest,cos_theta);
CROSS(temp,n,v);
MUL(temp,sin(phi));
ADD(dest,dest,temp);
COPY(temp,n);
MUL(temp,DOT(n,v)*(1-cos_theta));
ADD(dest,dest,temp);
}
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