Question

我正在尝试编写一些代码来计算正则多边形的面积，使用此公式（边*长度^ 2）/ 4 * tan（Pi / sides）我的代码看起来像

double area = (nSides * Math.pow(sLength, 2)) /
            4 * Math.tan ((Math.PI) / nSides);

我预计在nSides == 5和sLength == 6.5时，我应该得到72.69017017488385，但它输出38.370527260283126。

Answer 1

它被称为Order of Operations。 Java文档说不清楚here：

下表中的运算符按优先顺序列出

问题在于除法和乘法具有相同的优先级。

同一行上的运算符具有相同的优先级。 ...除了赋值运算符之外的所有二元运算符都是从左到右计算的;

因此，假设它们具有相同的优先级，则在乘以Math.tan之前将对除以4的除法进行求值。您需要通过插入一组额外的括号来明确指定顺序：

double area = (nSides * Math.pow(sLength, 2)) /
              (4 * Math.tan ((Math.PI) / nSides));

Answer 2

您需要为分母使用加法括号

(4 * Math.tan ((Math.PI) / nSides))

Else java认为你将整个表达式乘以Math.tan ((Math.PI) / nSides)。

double area = (nSides * Math.pow(sLength, 2)) /
         (4 * Math.tan ((Math.PI) / nSides));

Answer 3

如果任何人需要使用OOP概念计算正多边形的面积和周长，这是我的试验。有人问我这样的学校作业，这就是我试图解决的问题。我是一名学生，希望成为一名程序员，并乐于学习和分享知识。

正多边形是具有3个或更多边的形状。每一边的长度必须相等。计算面积的公式根据边数而不同。

方形区域=边长*边长;
三角形=边的长度*边的长度* sqrt（3）/ 4

在C＃中，我的代码似乎如下，但我尽可能地应用了oop的概念，并且我还实现了工厂设计模式。我也会用java编写代码。

这是IRegularPolygon接口，在这个问题中，我使用的是接口而不是抽象数据类型。

public interface IRegularPolygon
    {
        int NumberOfSides { get; set; }
        double SideLength { get; set; }
        double getPerimeter();
        double getArea();

    }
// you can also use abstract class the code is as follows 
public abstract class RegularPolygon
    {
        public int NumberOfSides { get; set; }
        public double SideLength { get; set; }
        public double getPerimeter()
        {
          return NumberOfSides * SideLength;
        }
        public double getArea();
    }

//The Square class that implement IRegularPolygon interface
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace RegularPolygon.BL
{
    public class Square : IRegularPolygon
    {
        public  int NumberOfSides { get; set; }
        public  double SideLength { get; set; }
        public Square(double SideLength)
        {
            this.NumberOfSides=4;
            this.SideLength = SideLength;
        }
        /// <summary>
        /// Get the Perimeter of the square
        /// </summary>
        /// <returns></returns>
        public double getPerimeter()
        {
            return NumberOfSides * SideLength;
        }
        /// <summary>
        /// Get the area of a square
        /// </summary>
        /// <returns></returns>
        public double getArea()
        {
            return SideLength * SideLength;
        }
        public override string ToString()
        {
            return String.Format("{0}-{1}", "Area of Sqare:" + getArea(), "Perimeter Of Sqaure :" + getPerimeter());
        }

    }
}

//The EquilateralTriangle class that implement IRegularPolygon interface
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace RegularPolygon.BL
{
    public class EquilateralTriangle : IRegularPolygon
    {
        public  int NumberOfSides { get; set; }
        public  double SideLength { get; set; }
        public EquilateralTriangle(double SideLength)
        {
            this.NumberOfSides=3;
            this.SideLength = SideLength;
        }
        /// <summary>
        /// Get the Perimeter of EquilateralTriangle
        /// </summary>
        /// <returns></returns>
        public double getPerimeter()
        {
            return NumberOfSides * SideLength;
        }
        /// <summary>
        /// Get the area of EquilateralTriangle
        /// </summary>
        /// <returns></returns>
        public double getArea()
        {
            return SideLength * SideLength * Math.Sqrt(3) / 4;
        }
        public override string ToString()
        {
            return String.Format("{0}-{1}", "Area of Sqare:" + getArea(), "Perimeter Of Sqaure :" + getPerimeter());
        }

    }
}

//The RegularPentagon class that implement IRegularPolygon interface
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace RegularPolygon.BL
{
    public class RegularPentagon : IRegularPolygon
    {
        public  int NumberOfSides { get; set; }
        public  double SideLength { get; set; }
        public double Apothem { get; set; }

        public RegularPentagon(double SideLength, double Apothem)
        {    
            this.NumberOfSides = 5;
            this.SideLength = SideLength;
            this.Apothem = Apothem;
        }
        /// <summary>
        /// Get the Perimeter of RegularPentagon
        /// </summary>
        /// <returns></returns>
        public double getPerimeter()
        {
            return NumberOfSides * SideLength;
        }
        /// <summary>
        /// Get the area of RegularPentagon
        /// </summary>
        /// <returns></returns>
        public double getArea()
        {
            return 2.5 * SideLength * Apothem;
        }
        public override string ToString()
        {
            return String.Format("{0}-{1}", "Area of Sqare:" + getArea(), "Perimeter Of Sqaure :" + getPerimeter());
        }

    }
}
// RegPolygonFactory class is a factory class that instantiate object based on shape 
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace RegularPolygon.BL
{
    public class RegPolygonFactory
    {
        /// <summary>
        /// Create instance of an object based on the type of shape 
        /// </summary>
        /// <param name="shapeType"></param>
        /// <param name="side"></param>
        /// <returns></returns>
        public IRegularPolygon getShape(string shapeType, double sideLength)
        {
            return getShape(shapeType, sideLength, 0.0);
        }
        public IRegularPolygon getShape(string shapeType, double sideLength, double apothem)
        {
            if (shapeType == null) throw new ArgumentNullException("shapeType");
            if (sideLength < 0.0) throw new ArgumentOutOfRangeException(sideLength.ToString());
            if (apothem < 0.0) throw new ArgumentOutOfRangeException(apothem.ToString());
            else if (shapeType.Equals("SQUARE"))
            {
                return new Square(sideLength);
            }
            else if (shapeType.Equals("EQUILATERALTRIANGLE"))
            {
                return new EquilateralTriangle(sideLength);
            }
            //shapeType.equalsIgnoreCase("REGULARPENTAGON")
            else if (shapeType.Equals("REGULARPENTAGON"))
            {
                return new RegularPentagon(sideLength, apothem);
            }
            return null;
        }


    }
}

//For unit Test: To test for instance square
using System;
using System.Text;
using System.Collections.Generic;
using System.Linq;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using RegularPolygon.BL;

namespace RegularPolygonTest.BL
{
    [TestClass]
    public class SquareTest
    {
        RegPolygonFactory regularPolygon = new RegPolygonFactory();

        /// <summary>
        /// Test the Area Of Square with valid input(side=4)
        /// </summary>
        [TestMethod]
        public void getAreaOfSquare_ValidArgument()
        {
            //Arrange
            double sideLength = 4;
            var square = regularPolygon.getShape("SQUARE", sideLength);
            var expected = sideLength * sideLength;
            //Act
            var actual = square.getArea();

            //Assert
            Assert.AreEqual(expected, actual);
        }
    /// <summary>
        /// Test the Perimeter Of Square with valid input(side=6, edges=4)
        /// </summary>
        [TestMethod]
        public void getPerimeterOfSquare_ValidAregument()
        {
            //Arrange
            double sideLength = 6;
            double NumberOfSides = 4;
            var square = regularPolygon.getShape("SQUARE", sideLength);
            var expected = sideLength * NumberOfSides;
            //Act
            var actual = square.getPerimeter();

            //Assert
            Assert.AreEqual(expected, actual);
        }
        /// <summary>
        /// Test the Perimeter Of Square with invalid input(edges=6)
        /// </summary>
        [TestMethod]
        public void getPerimeterOfSquare_InValidPostiveAregument()
        {
            //Arrange
            double sideLength = 5;
            double NumberOfSides = 6;
            var square = regularPolygon.getShape("SQUARE", sideLength);
            var expected = sideLength * NumberOfSides;
            //Act
            var actual = square.getPerimeter();

            //Assert
            Assert.AreEqual(expected, actual);
        }
  }
}

计算正多边形问题的面积

3 个答案: