Java-余弦-递推

C语言实验——余弦

Time Limit: 1000 ms  Memory Limit: 65536 KiB

Submit  Statistic

Problem Description

输入n的值，计算cos(x)。 

Input

输入数据有多行，每行两个数，包括x和n。第一数据为x，第二个数据为n。

Output

输出cos(x)的值，保留4位小数。

Sample Input

0.0 100

Sample Output

1.0000

Hint

递推：

import java.util.Scanner;  
  public class Main {  
		public static void main(String[] args) {  
			Scanner sc = new Scanner(System.in);
			while(sc.hasNext()) {
				double x = sc.nextDouble();
				double n = sc.nextDouble();
				double sum = 0.0, flag = 1.0, s = 1.0;
				
				for(int i = 0; i <= n; i++) {
					if(i != 0) {
						s = s * (x * x) * 1.0 / ((2 * i)* (2 * i - 1));
					}
					sum += (s * flag);
					flag = -flag;
				}
				System.out.println(String.format("%.4f", sum));
			}
			sc.close();
		}
}  

公式法：

import java.util.Scanner;  
  public class Main {  
		public static void main(String[] args) {  
			Scanner sc = new Scanner(System.in);
			while(sc.hasNext()) {
				double x = sc.nextDouble();
				double n = sc.nextDouble();
				double sum = 1;
				double x1, x2;
				for(int i = 1; i <= n; i++) {
					double t = 1;
					for(int j = 1; j <= 2 * i; j++) {
						t *= j;
					}
					sum += Math.pow(x, 2*i)/(t *Math.pow(-1, i));
				}
				System.out.println(String.format("%.4f", sum));
			}
			sc.close();
		}
}