line calculations using its known coordinates

Hello every one

How to calculate the angle between two lines (lines have known coordinates)

Thanks

Answer 1

[William Rose]

Suppose slope of line 1 is a1 and slope of line 2 is a2. Then angle of line 1 relative to x axis is theta1=arctan(a1) and angle of line 2 is theta2=arctan(a2). Angle between lines is theta1-theta2.

[William Rose]

In Matlab, the arctan function is atan().