HDU 4969 Just a Joke

题目链接

推公式，r′=dr/dt=vy=v22?v12r2/R2????????????√,可得积分公式为
∫R0y=1/v22?v12x2/R2?????????????√，利用三角换元去化简即可

代码：

#include 
  
   
#include 
   
     #include 
    
      typedef long long ll; int t; double v1, v2, r, d; int main() { scanf("%d", &t); while (t--) { scanf("%lf%lf%lf%lf", &v1, &v2, &r, &d); double ti = asin(r * v1 / r / v2) * r / v1 - asin(0.0) * r / v1; if (ti * v2 > d) printf("Why give up treatment\n"); else printf("Wake up to code\n"); } return 0; }