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 a_{1}, b_{1}, c_{1} and a_{2}, b_{2}, c_{2} is given by

Given -

a_{1} = a, b_{1} = b, c_{1} = c

a_{2} = b - c, b_{2} = c - a, c_{2} = a - b

So,

= 0

∴ cosθ = 0

So, θ = 90°

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

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