+void normalise(double v[D3], double one, double absepsilon) {
+ int k;
+ double multby= one/(magnD(v) + absepsilon);
+ K v[k] *= multby;
+}
+
+void xprod_norm(double r[D3], const double a[D3], const double b[D3],
+ double one, double absepsilon) {
+ xprod(r,a,b);
+ normalise(r, absepsilon, one);
+}
+
+double dotprod(const double a[D3], const double b[D3]) {
+ int k;
+ double result= 0;
+ K result += a[k] * b[k];
+ return result;
+}
+