Find the angle between the lines whose direction ratios are a, b, c and b – c, c – a, a – b.

Angle between the lines with direction ratios a₁, b₁, c₁ and a₂, b₂, c₂ is given by

Given -

a₁ = a, b₁ = b, c₁ = c

a₂ = b - c, b₂ = c - a, c₂ = a - b

So,

= 0

∴ cosθ = 0

So, θ = 90°

Hence, Angle between the given pair of Lines is 90°.