C＃数学，给出了错误的结果 [英] C# math, giving wrong result

问题描述

我的代码：

My code:

using System;

namespace PolarToCart
{
	class Program
	{
		static void Main(string[] args)
		{
			double r;
			double θ;
			double ϕ;

			string result = "";

			r = 1.0;
			θ = 2.0;
			ϕ = 3.0;

			result = Convert.ToString(
					r * Math.Sin(θ) * Math.Cos(ϕ)
				);

			Console.WriteLine(result);
			Console.ReadKey();
		}
	}
}

给我结果：



-0.900197629735517



但是，在我的计算器（和其他计算器）上计算的正确结果是：



0.03485166816



我不知道这里发生了什么。有人有什么见解吗？



谢谢！



我的尝试：



我试图尝试使用括号，而我的数学 - 更好的一半，（有一些编程经验），也是难过的。一些谷歌搜索是自然尝试的

Gives me the result:

-0.900197629735517

However, the correct result, when it's calculated on my calculator, (and other calculators), is:

0.03485166816

I've no idea what's going on here. Does somebody have any insights?

Thank you!

What I have tried:

I've tried to experiment with parenthesizes, and my math-wiz better half, (who has had some programming experience), is also stumped. Some googling was naturally tried

推荐答案

三角函数的参数是弧度。如果您的输入是度数，则必须除以2 * Pi：

The arguments to the trigonometric functions are in radians. If your input is in degrees, you must divide by 2 * Pi:

result = Convert.ToString(
            r * Math.Sin(θ / (2 * Math.PI)) * Math.Cos(ϕ / (2 * Math.PI))
        );

使用了错误因素。

Used thew wrong factor.

result = Convert.ToString(
    r * Math.Sin(Math.PI / 180 * θ) * Math.Cos(Math.PI / 180 * ϕ)
);

[/ EDIT]

[/EDIT]

我同意它： https://www.wolframalpha.com/input/?i=1.0+*+Sin（2.0）+ * + Cos（3.0） [ ^ ]

Wolfram alpha同意。

和我的计算器一样（夏普EL-5020）



你确定吗你的计算器不是假设θ和φ是度，而不是弧度，比如我的计算器，Wolfram Alpha和.NET？

And I'd agree with it: https://www.wolframalpha.com/input/?i=1.0+*+Sin(2.0)+*+Cos(3.0)[^]
Wolfram alpha agrees.
As does my calculator (Sharp EL-5020)

Are you sure your calculators aren't assuming that θ and ϕ are in degrees, rather than radians, like my calculator, Wolfram Alpha, and .NET?

固定代码：

The fixed code:

using System;

namespace PolarToCart
{
	class Program
	{
		public double ConvertToRadians(double angle)
		{
			return (Math.PI / 180) * angle;
		}

		static void Main(string[] args)
		{
			double r;
			double θ;
			double ϕ;

			string result = "";

			r = 1.0;
			θ = 2.0;
			ϕ = 3.0;

			result = Convert.ToString(

				r * Math.Sin((Math.PI / 180) * θ) * Math.Cos((Math.PI / 180) * ϕ)
				);

			Console.WriteLine(result);

			Console.ReadKey();
		}
	}
}

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