在Trianglele类中定义三个Point的实体来表示一个三角形的三个点，再定义一个方法setTri对这三个点进行初始化，然后定义两个方法求三角形的周长、面积。在main()中创建一个对象，求给定三点的三角形的周长、面积。-Trianglele categories defined in the Point of the three entities to express a triangle of three points, and then define a method setTri to initialize the three points, and then the definition of two methods for triangular perimeter, area. In the main () to create an object, and given three points of the triangle of perimeter, area.