HDU 4969 Just a Joke（积分)

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 <cstdio>#include <cstring>#include <cmath>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;}