在圆上找到点的角度 [英] Find angle of point on circle

问题描述

想象一下，我在屏幕上绘制了一个中心坐标为(cx，cy)的圆，并在该圆上选择了一个随机点(A).

Imagine I have drawn a circle with center coordinates (cx,cy) on the screen and a random point (A) is selected on the circle.

通过具有点A的坐标，我需要找到(a)的角度.

By having the the coordinates of point A, I need to find the angle of (a).

更新:

我尝试使用以下公式:

Math.toDegrees(Math.asin(((x - cx) / radius).toDouble()))

实际上与之相反(圆是通过向该圆角进给而创建的):

which is actually the reverse of (the circle is created by feeding angles to this one):

x = radius * Math.sin(Math.toRadians(angle.toDouble())) + cx
y = radius * Math.cos(Math.toRadians(angle.toDouble())) + cy

但是由于公式中不存在y坐标，因此答案可能是错误的.

But since the y coordinate is not present in the formula the answer could be wrong.

推荐答案

如果知道点A(x，y)的笛卡尔坐标，则可以通过将其转换为极坐标来找到角度theta，如下所示:

If you know the cartesian coordinates of the point A(x,y), then you can find the angle theta by converting it into polar coordinates as below:

double theta = Math.toDegrees(Math.atan2(y - cy, x - cx));

如果您的X轴为0度，则此公式有效，否则需要考虑偏移量.

This formula works if your X axis is in 0 degrees, otherwise you need to consider the offset.

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