62 lines
1.2 KiB
C++
62 lines
1.2 KiB
C++
#include<stdio.h>
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#include<cmath>
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double x,y,v;
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const double g=9.8;
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double f(double a)
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{
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return x*tan(a)-x*x*g/(2*v*v*cos(a)*cos(a));
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}
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double sanf(double bottom,double top)
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{
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double rightthir,leftthir;
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while(top-bottom>1e-9)
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{
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rightthir=(bottom+top*2)/3;
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leftthir=(bottom*2+top)/3;
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if(f(rightthir)>f(leftthir))
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{
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bottom=leftthir+1e-10;
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}
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else
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{
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top=rightthir-1e-10;
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}
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}
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return (top+bottom)/2;
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}
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double erfen(double bottom,double top)
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{
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double mid;
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while(top-bottom>1e-9)
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{
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mid=(top+bottom)/2;
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if(f(mid)>y)
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{
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top=mid-1e-10;
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}
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else
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{
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bottom=mid+1e-10;
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}
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}
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return (bottom+top)/2;
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}
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int main()
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{
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int t;
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scanf("%d",&t);
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while(t--)
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{
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scanf("%lf%lf%lf",&x,&y,&v);
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double max=sanf(0,3.1415926535897932384626433832795/2.0);
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if(f(max)<y)
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{
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printf("-1\n");
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}
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else
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{
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printf("%.6lf\n",erfen(0,max));
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}
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}
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}
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