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Question
Find the angle between the lines whose direction ratios are a, b, c and b − c, c − a, a − b.
Solution
the angle between the given lines is given by
cos θ = `(a(b - c) + b(c - a) + c(a - b))/(sqrt(a^2 + b^2 + c^2). sqrt((a - b)^2 + (b - c)^2 + (c - a)^2)`
cos θ = 0
⇒ Hence, θ = 90°
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