Given lines are x + y = 1 and x + y = 1.

Slope of line (1) is m₁ = -√3, while the slope of line (2) is m₂ = -1/√3

Let θ be the angle between two lines

∴ θ = 30°

Thus the angle between the given lines is either 30° or 180° - 30° = 150°