Angle between two lines in terms of slope of the lines
You can see two intersecting lines (a and b) in red. Equation of the lines is written in slope intercept form(y=mx+c). Line ‘a’ makesan angle α with the positive direction of x axis(shown in blue color)and line ‘b’ makes an angle β with the positive direction of x axis(shown in blue color). A is a free point on line a and B is a free point in line b. You can move these points. Angle between these two lines (У) is also shown in black color