# How to measure angle of intersection ?

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thineesh Vijayakumar on 9 Apr 2019
Commented: A. Sawas on 12 Apr 2019
I need to calculate the angle of intersection . Can anyone share the coding ? How to find the angle (red shaded region) ? Thank you. Rik on 9 Apr 2019
Do you have the locations of the two lines involved? Then you could fit two linear functions and use mathematics to find the angle.
A. Sawas on 9 Apr 2019
I think you have asked an identical question before "How to measure angle between two lines?".
I reposted the solution below and added some comments. Please comment on the solution if this is not what you are looking for.

A. Sawas on 9 Apr 2019
Edited: A. Sawas on 9 Apr 2019
Assuming that the two lines are defined by four points P1, P2, P3, and P4 as such, the first line is L1(P1,P2) and the second line L2 (P3,P4) you can find the angle using the following code:
% define the points as [x,y]
P1 = [1,1];
P2 = [5,5];
P3 = [5,2];
P4 = [1,3];
% dx = x1 - x2;
dx1 = P1(1)-P2(1);
dx2 = P3(1)-P4(1);
% dy = y1 - y2;
dy1 = P1(2)-P2(2);
dy2 = P3(2)-P4(2);
% the angle (in degrees) between the lines:
angle = 180 - acosd((dx1*dx2+dy1*dy2)/(sqrt(dx1^2+dx2^2)*sqrt(dy1^2+dy2^2)));
disp(angle);

thineesh Vijayakumar on 12 Apr 2019
Thank you :)
A. Sawas on 12 Apr 2019
You are welcome :)