?湘大oj題目地址：傳送門

Cycloid

時間限制： 1000?ms ?|? 內存限制： 65536 KB

Description

A?cycloid?is the curve traced by a point on the rim of a circular wheel as the wheel rolls along a straight line. It is an example of a roulette, a curve generated by a curve rolling on another curve.

????????????????????????????????????????????????????????????????????????????????????????????????????????????????--from wikipedia

Please calculate the area of an arch of a cycloid generated by a circle of radius?r.

You may define pi as acos(-1.0).

?

Input

?????????The first line of the input consists of a single integer K (1 <= K <= 1,000), denoting the number of test cases. Then K lines follow, each contains a real number r (0.0 < r < 1e3), indicating the radius of circle.

?

Output

?????????For each test case, output a line containing one real number with exactly three digits after the decimal point, indicating the area of an arch.

?

Sample Input

2

1.0

3.5

?

Sample Output

9.425

115.454

============================傲嬌的分割線============================

題目意思：求圓走過的那一部分弧線所圍成的面積，這個有一個公式，擺線留下的面積等于圓的三倍

#include <stdio.h> #include<iostream> #include<math.h> using namespace std; int main(){int n;double r;scanf("%d",&n);while(n--){cin>>r;double x=3*acos(-1.0)*r*r;printf("%.3f\n",x);}}

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