How to measure angle between two lines?

How to measure the angle ? Can anyone share coding. Thank you

Answer 1

[A. Sawas]

P1 = [1,1];
P2 = [5,5];
P3 = [5,2];
P4 = [1,3];
xL1 = P1(1)-P2(1);
xL2 = P3(1)-P4(1);
yL1 = P1(2)-P2(2);
yL2 = P3(2)-P4(2);
angle = 180 - acos((xL1*xL2+yL1*yL2)/(sqrt(xL1^2+xL2^2)*sqrt(yL1^2+yL2^2)))*180/pi;

figure;
plot([P1(1),P2(1)],[P1(2),P2(2)],'-+'); hold on;
plot([P3(1),P4(1)],[P3(2),P4(2)],'-*');

[thineesh Vijayakumar]

Thank you but the angle value doesnt appear.

[A. Sawas]

The value is in the variable angle

disp(angle)