#include <iostream>
using namespace std;double fact(int x)	//定義階乘函數。注意是double類型
{double y = x;	//注意是double類型for (int i = x-1; i > 0; i--)y *= i;return y;
};double My_sin(int x)	//定義sin函數。注意是double類型
{double y = 0;	//注意是double類型int i = 1;double n = pow(x, i) / fact(i);	//初始化n的值為第一項的值。注意不能賦值為0，否則while循環不執行while (n > 1e-6)	//多項式n的值小于10^6時停止循環（數值已收斂）{n = pow(x, i) / fact(i);if (i % 4 == 1)y += n;else if (i % 4 == 3)y -= n;i++;};return y;
};double fun_k(float r, float s)	//定義函數。注意是double類型
{double k;	//注意是double類型if (pow(r, 2) <= pow(s, 2))k = pow((pow(My_sin(r), 2) + pow(My_sin(s), 2)), 0.5);else k = 0.5 * sin(r * s);return k;
}int main() 
{float r, s ,k;cout << "Please input value of r:" << endl;cin >> r;cout << "Please input value of s:" << endl;cin >> s;k = fun_k(r, s);cout << "value of k is:" << k;
}