HDU 4969 Just a Joke

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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就可以

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;

}