WOLFRAM|DEMONSTRATIONS PROJECT

Measure of the Angle between Two Straight Lines

​
The angle between the lines is 55.41°.
The angle between the two lines is given by
θ=β-α
.
Let
y=
m
1
x+
b
1
and
y=
m
2
x+
b
2
be the equations of two lines in the plane, with
m
1
and
m
2
the slopes of the lines. The angle
θ
between them is given by
θ=
-1
tan
m
1
-
m
2
1+
m
1
m
2
.