23 lines
490 B
C++
23 lines
490 B
C++
#include<cstdio>
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#include<cmath>
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double pi=acos(-1),lon,lonn,lonx,le=0,ri,mi,deg,h,ans;
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#define d_r(a) (pi/180.0*(a))
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#define r_d(a) (180.0/pi*(a))
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int main()
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{
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scanf("%lf%lf%lf",&lon,°,&h);
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lonn=(1+deg*h)*lon;
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ri=d_r(180);
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if(lon*deg*h==0) {printf("0.000\n");return 0;}
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while(ri-le>0.00000000001)
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{
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mi=(le+ri)/2;
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lonx=2*((lon/2)/sin(mi/2))*pi*mi/d_r(360);
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if(lonx>=lonn) ri=mi;
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else le=mi;
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}
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ans=(lon/2)/sin(mi/2)-(lon/2)/tan(mi/2);
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printf("%.3lf\n",ans);
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return 0;
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}
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