杭电多校第六场 oval-and-rectangle（数学积分）

oval-and-rectangle Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others) Total Submission(s): 876    Accepted Submission(s): 380   Problem Description Patrick Star find an oval. The half of longer axes is on the x-axis with length a. The half of shorter axes is on the y-axis with length b. Patrick Star plan to choose a real number c randomly from [0,b], after that, Patrick Star will get a rectangle : 1. The four vertexes of it are on the outline of the oval. 2. The two sides of it parallel to coordinate axis. 3. One of its side is y=c. Patrick Star want to know the expectations of the rectangle's perimeter.   Input The first line contain a integer T (no morn than 10), the following is T test case, for each test case : Each line contains contains two integer a, b (0<b<a<105). Separated by an white space.   Output For each test case output one line denotes the expectations of the rectangle's perimeter . You should keep exactly 6 decimal digits and ignore the remain decimal digits.  It is guaranted that the 7-th decimal digit of answer wont be 0 or 9.   Sample Input 1 2 1   Sample Output 8.283185   Source 2018 Multi-University Training Contest 6   Recommend chendu   |   We have carefully selected several similar problems for you:  6373 6372 6371 6370 6369    Statistic | Submit | Discuss | Note

积分

#include <bits/stdc++.h>

using namespace std;

#define pi acos(-1.0)

int main(void)
{
    int T;
    cin >> T;
    double ans;
    while(T--) {
        double a,b;
        cin >> a >> b;
        ans = a * pi + 2 * b;
        ans -= 0.0000005;
        printf("%.6lf\n",ans);
    }
    return 0;
}