计算三角形面积

解题思路:

注意事项:

参考代码:

public class Main {

    public static void main(String[] args) {

     Scanner sc=new Scanner(System.in);

        double x1=sc.nextDouble();

        double y1=sc.nextDouble();//定义第一个点的坐标

        double x2=sc.nextDouble();

        double y2=sc.nextDouble();//定第二个点的坐标

        double x3=sc.nextDouble();

        double y3=sc.nextDouble();//定义第三个点的坐标

//知道点的坐标，则AB之间的距离为√[(X1－X2)^2+(Y1－Y2)^2]

//求根的方法：Math.sqrt();

//计算每两点之间的距离

        double first = Math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));

        double second =  Math.sqrt((x2-x3)*(x2-x3)+(y2-y3)*(y2-y3));

        double third = Math.sqrt((x3-x1)*(x3-x1)+(y3-y1)*(y3-y1));

  //计算三角形的面积

        double s = (first+second+third)/2;

        double area = Math.sqrt(s*(s-first)*(s-second)*(s-third));

        System.out.printf("%.2f",area);

    }

}