C# 中的 Math.Atan2 或类实例问题
这是我的问题（C#）：
double Y = 0.0;
double X = -21.0;
double q1_Test = Math.Atan2(0.0, -21.0); // gives Math.Pi
double q1_Test2 = Math.Atan2(( double)Y, (double)X); // gives Math.Pi
double w1 = <SomeclassInstanceGlobalHere>.getW1(); // This is a class which updates a variable
double w2 = <SomeclassInstanceGlobalHere>.getW2(); // This is a class which updates a variable
double q1 = Math.Atan2(w2, w1); // ** gives -Math.Pi ** ???
//w2 shows 0.0 and w1 shows -21.0
当我从另一个类获取值时，变量值分别为 0.0 和 -21.0。调试时它也会显示在 IDE 中。 这里出了什么问题？
Here is my problem (C#) :
double Y = 0.0;
double X = -21.0;
double q1_Test = Math.Atan2(0.0, -21.0); // gives Math.Pi
double q1_Test2 = Math.Atan2(( double)Y, (double)X); // gives Math.Pi
double w1 = <SomeclassInstanceGlobalHere>.getW1(); // This is a class which updates a variable
double w2 = <SomeclassInstanceGlobalHere>.getW2(); // This is a class which updates a variable
double q1 = Math.Atan2(w2, w1); // ** gives -Math.Pi ** ???
//w2 shows 0.0 and w1 shows -21.0
When I get the values from the other class, variable values are 0.0 and -21.0 respectively. It also shows in the IDE while debugging.
What is going wrong here?
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w2 实际上必须为 -0.0，其格式为 0
以下博客文章展示了如何实际测试此值 (Decimal.GetBits(value))：
http:// blogs.msdn.com/bclteam/archive/2006/10/12/decimal-negative-zero-representation-lakshan-fernando.aspx
w2 must actually be -0.0, which is formatted as 0
The following blog post shows how you can actually test for this (Decimal.GetBits(value)):
http://blogs.msdn.com/bclteam/archive/2006/10/12/decimal-negative-zero-representation-lakshan-fernando.aspx
请注意，对于三角学而言，-Math.PI 和 Math.PI 是等效的。将角度当作双倍角度进行比较几乎总是一个非常糟糕的主意。请参阅扩展的 SO 讨论：再次平均角度
Note that -Math.PI and Math.PI are equivalent for the purposes of trigonometry. It is almost always a very poor idea to compare angles as if they were doubles. See extended SO discussion: Averaging angles... Again