31 lines
718 B
C
31 lines
718 B
C
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#include <math.h>
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float bessy0(x)
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float x;
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{
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float bessj0();
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float z;
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double xx,y,ans,ans1,ans2;
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if (x < 8.0) {
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y=x*x;
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ans1 = -2957821389.0+y*(7062834065.0+y*(-512359803.6
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+y*(10879881.29+y*(-86327.92757+y*228.4622733))));
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ans2=40076544269.0+y*(745249964.8+y*(7189466.438
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+y*(47447.26470+y*(226.1030244+y*1.0))));
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ans=(ans1/ans2)+0.636619772*bessj0(x)*log(x);
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} else {
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z=8.0/x;
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y=z*z;
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xx=x-0.785398164;
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ans1=1.0+y*(-0.1098628627e-2+y*(0.2734510407e-4
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+y*(-0.2073370639e-5+y*0.2093887211e-6)));
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ans2 = -0.1562499995e-1+y*(0.1430488765e-3
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+y*(-0.6911147651e-5+y*(0.7621095161e-6
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+y*(-0.934945152e-7))));
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ans=sqrt(0.636619772/x)*(sin(xx)*ans1+z*cos(xx)*ans2);
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}
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return ans;
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}
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