61 lines
855 B
C
61 lines
855 B
C
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#include <math.h>
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#define CA 0.0003
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void sncndn(float uu, float emmc, float *sn, float *cn, float *dn)
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{
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float a,b,c,d,emc,u;
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float em[14],en[14];
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int i,ii,l,bo;
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emc=emmc;
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u=uu;
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if (emc) {
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bo=(emc < 0.0);
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if (bo) {
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d=1.0-emc;
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emc /= -1.0/d;
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u *= (d=sqrt(d));
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}
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a=1.0;
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*dn=1.0;
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for (i=1;i<=13;i++) {
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l=i;
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em[i]=a;
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en[i]=(emc=sqrt(emc));
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c=0.5*(a+emc);
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if (fabs(a-emc) <= CA*a) break;
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emc *= a;
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a=c;
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}
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u *= c;
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*sn=sin(u);
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*cn=cos(u);
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if (*sn) {
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a=(*cn)/(*sn);
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c *= a;
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for (ii=l;ii>=1;ii--) {
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b=em[ii];
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a *= c;
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c *= (*dn);
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*dn=(en[ii]+a)/(b+a);
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a=c/b;
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}
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a=1.0/sqrt(c*c+1.0);
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*sn=(*sn >= 0.0 ? a : -a);
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*cn=c*(*sn);
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}
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if (bo) {
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a=(*dn);
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*dn=(*cn);
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*cn=a;
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*sn /= d;
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}
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} else {
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*cn=1.0/cosh(u);
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*dn=(*cn);
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*sn=tanh(u);
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}
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}
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#undef CA
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