blocks|key|1305422|text|因为我相信它与arctan(y/x)有关，所以y出现在顶部。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1305423|这里有一个关于它的很好的链接：Angles+and+Directions|offset|length|1305424|entityMap|0|LINK|mutability|MUTABLE|url|http://wiki.tcl.tk/10814^0|0|F|L|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@$D|P|E|Q|1|R]]|A|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|M]]]]

Because I believe it is related to arctan(y/x), so y appears on top.

Here's a nice link talking about it a bit: <a href="http://wiki.tcl.tk/10814" rel="noreferrer">Angles and Directions</a>

blocks|key|1305455|text|我一直认为这是因为trig的定义，即|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1305456|tan(theta)+=+opposite+/+adjacent|code-block|syntax|javascript|1305457|使用从原点开始的标准角度时，相对方向始终为Y，相邻方向始终为X，因此：|1305458|atan2(opposite,+adjacent)+=+theta|1305459|也就是说，它是这样做的，所以在数学定义方面没有顺序混乱。|1305460|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

My assumption has always been that this is because of the trig definition, ie that 

<pre><code>tan(theta) = opposite / adjacent
</code></pre>

When working with the canonical angle from the origin, opposite is always Y and adjacent is always X, so:

<pre><code>atan2(opposite, adjacent) = theta
</code></pre>

Ie, it was done that way so there's no ordering confusion with respect to the mathematical definition.

blocks|key|1520523|text|假设有一个矩形三角形，其相对边称为y，相邻边称为x：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1520524|tan(角度)=+y/x|1520525|arctan(tan(角度))=+arctan(y/x)|1520526|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

Suppose a rectangle triangle with its opposite side called y, adjacent side called x:

tan(angle) = y/x

arctan(tan(angle)) = arctan(y/x)

blocks|key|1520560|text|excel中的顺序是atan2(X，Y)，所以我认为相反的顺序是编程的事情。atan(Y/X)可以很容易地更改为atan2(Y，X)，方法是在“n”和“(”之间放置一个“2”，并将“/”替换为“，”，只有2个操作。相反的顺序需要4次操作，一些操作会更复杂(剪切和粘贴)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1520561|我经常在Excel中计算出我的数学，然后将其移植到.NET，所以有时会在atan2上挂掉。如果atan2能够以某种方式标准化，那将是最好的。|1520562|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

The order is atan2(X,Y) in excel so I think the reverse order is a programming thing. atan(Y/X) can easily be changed to atan2(Y,X) by putting a '2' between the 'n' and the '(', and replacing the '/' with a ',', only 2 operations. The opposite order would take 4 operations and some of the operations would be more complex (cut and paste).

I often work out my math in Excel then port it to .NET, so will get hung up on atan2 sometimes. It would be best if atan2 could be standardized one way or the other.

blocks|key|1520583|text|如果atan2的论点颠倒过来，那会更方便。这样你就不需要担心在计算极轴角度时会翻转参数。Mathematica的等价物就是这样做的：https://reference.wolfram.com/language/ref/ArcTan.html|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1520584|很久以前，FORTRAN有一个ATAN2函数，它的参数顺序不太方便，在this+reference+manual中，它被(有点不准确地)描述为arctan(arg1+/+arg2)。|1520585|看似合理的是，最初的创建者专注于atan2(arg1，arg2)+(或多或少)+arctan(arg1+/+arg2)，并且决定被盲目地从FORTRAN语言复制到C语言，复制到C%2B%2B、Python、Java和JavaScript。|1520586|entityMap|0|LINK|mutability|MUTABLE|url|https://reference.wolfram.com/language/ref/ArcTan.html|1^0|1U|1I|0|0|Z|L|1|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|6|7|U|8|@]|9|@$A|V|B|W|1|X]]|C|$]]|$1|F|3|G|5|6|7|Y|8|@]|9|@]|C|$]]|$1|H|3|-4|5|6|7|Z|8|@]|9|@]|C|$]]]|I|$J|$5|K|L|M|C|$N|O]]|P|$5|K|L|M|C|$N|O]]]]

It would be more convenient if atan2 had its arguments reversed. Then you wouldn't need to worry about flipping the arguments when computing polar angles. The Mathematica equivalent does just that: <a href="https://reference.wolfram.com/language/ref/ArcTan.html" rel="nofollow noreferrer">https://reference.wolfram.com/language/ref/ArcTan.html</a>

Way back in the dawn of time, FORTRAN had an ATAN2 function with the less convenient argument order that, in <a href="https://reference.wolfram.com/language/ref/ArcTan.html" rel="nofollow noreferrer">this reference manual</a>, is (somewhat inaccurately) described as arctan(arg1 / arg2). 

It is plausible that the initial creator was fixated on atan2(arg1, arg2) being (more or less) arctan(arg1 / arg2), and that the decision was blindly copied from FORTRAN to C to C++ and Python and Java and JavaScript.

In C the atan2 function has the following signature:

<pre><code>double atan2( double y, double x );
</code></pre>

Other languages do this as well. This is the only function I know of that takes its arguments in Y,X order rather than X,Y order, and it screws me up regularly because when I think coordinates, I think (X,Y).

Does anyone know why atan2's argument order convention is this way?

Why are the arguments to atan2 Y,X rather than X,Y?

Python

Java

在C中，atan2函数具有以下签名：double atan2( double y, double x );其他语言也是这样做的。这是我所知道的唯一一个以Y，X顺序而不是X，Y顺序为参数的函数，它经常把我搞砸，因为当我考虑坐标时，我认为是(X，Y)。有人知道为什么atan2的参数顺序约定是这样的吗？

问为什么atan2的参数是Y，X而不是X，Y？
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