# Measure of the Angle between Two Straight Lines

Measure of the Angle between Two Straight Lines

The angle between the two lines is given by .

θ=β-α

Let and be the equations of two lines in the plane, with and the slopes of the lines. The angle between them is given by

y=x+

m

1

b

1

y=x+

m

2

b

2

m

1

m

2

θ

θ=-

-1

tan

m

1

m

2

1+

m

1

m

2