calculating angle between three points

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KalMandy 2017-3-21

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https://ww2.mathworks.cn/matlabcentral/answers/331017-calculating-angle-between-three-points

编辑： clarammd 2023-4-23

angle = atan2(abs(det([P2-P0;P1-P0])),dot(P2-P0,P1-P0));

I have seen that the angle between three points can be calculated as above where P0 = [x0,y0], P1 = [x1,y1], and P2 = [x2,y2]

can someone tell me at which point is this angle calculated? OR any other code which does the same thing is also appreciated. Thanks

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Bjorn Gustavsson 2017-3-21

Well, why not give it a try? Put down 3 points on a paper in a triangle, use them as an input to the expression and see what it gives you. After that you should be able to figure out the answer.

HTH

KalMandy 2017-3-21

Thanks. I know that I can try that, but I wanted to see other options too.

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Answer 1

Jan 2017-3-21

4
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/331017-calculating-angle-between-three-points#answer_259649

编辑：Jan 2017-3-21

在 MATLAB Online 中打开

The shown code calculates the angle between the lines from P0 to P1 and P0 to P2.

Neither the dot nor the cross product are stable. This means that there are some inputs for both command, which reply inaccurate output:

P0 = [x0, y0];
P1 = [x1, y1];
P2 = [x2, y2];
n1 = (P2 - P0) / norm(P2 - P0);  % Normalized vectors
n2 = (P1 - P0) / norm(P1 - Po);
angle1 = acos(dot(n1, n2));                        % Instable at (anti-)parallel n1 and n2
angle2 = asin(norm(cropss(n1, n2));                % Instable at perpendiculare n1 and n2
angle3 = atan2(norm(cross(n1, n2)), dot(n1, n2));  % Stable