如何计算从垂直矢量的角度θ [英] How to calculate the angle of a vector from the vertical?

问题描述

我试着找了两次二维向量的夹角（度）。我知道我需要使用触发，但我不太好它。这就是我试图找出（Y轴向下增加）：

Im trying to find out the angle (in degrees) between two 2D vectors. I know I need to use trig but I'm not too good with it. This is what I'm trying to work out (the Y axis increases downward):

我试图用这个code的时刻，但它不工作（计算任意角度出于某种原因）：

I'm trying to use this code at the moment, but it's not working at all (calculates random angles for some reason):

private float calcAngle(float x, float y, float x1, float y1)
{
    float _angle = (float)Math.toDegrees(Math.atan2(Math.abs(x1-x), Math.abs(y1-y)));
    Log.d("Angle","Angle: "+_angle+" x: "+x+" y: "+y+" x1: "+x1+" y1: "+y1);
    return _angle;
}

（提供恒定的位置时，有恒定的，但是当我改变位置，角度的变化，我无法找到两个角度之间的任何链接）这是我的结果：

These are my results (There constant when providing a constant position, but when I change the position, the angle changes and I can't find any link between the two angles):

位置1： X：100 Y：100 X1：50 Y1：50 角度：45

Position 1: x:100 y:100 x1:50 y1:50 Angle: 45

位置2： X：92 Y：85 X1：24 Y1：16 角度：44.58

Position 2: x:92 y:85 x1:24 y1:16 Angle: 44.58

位置3： X：44 Y：16 X1：106 Y1：132 角度：28.12

Position 3: x:44 y: 16 x1:106 y1:132 Angle: 28.12

编辑：谢谢大家谁回答和帮助我弄清楚，错了！对不起标题和问题混淆了。

Thanks everyone who answered and helped me figure out that was wrong! Sorry the title and the question was confusing.

推荐答案

啊哈！原来我只是需要我的翻转角度和使用ATAN2。这是我最后的code：

Aha! Turns out I just needed to flip my angle and use atan2. This is my final code:

private float calcAngle(float x, float y, float x1, float y1)
{
    float _angle = (float)Math.toDegrees(Math.atan2(x1-x, y-y1));
    return _angle;
}

谢谢大家帮助我弄清楚了这一点，同时也帮助我了解我实际上做！ ：）

Thanks everyone for helping me figure this out and also for helping me to understand what I'm actually doing! :)

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