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CUET · MATHS · PYQ PAPER 2025

If the direction ratios of two lines are \(a, b, c\) and \((b-c),(c-a),(a-b)\) respectively, then the angle between these lines is :

  1. A \(\frac{\pi}{4}\)
  2. B \(\frac{\pi}{3}\)
  3. C \(\frac{\pi}{2}\)
  4. D \(\frac{2 \pi}{3}\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(\frac{\pi}{2}\)

Step-by-step Solution

Detailed explanation

\(\cos \theta = \frac{a(b-c) + b(c-a) + c(a-b)}{\sqrt{a^2+b^2+c^2}\sqrt{(b-c)^2+(c-a)^2+(a-b)^2}}\) \(\cos \theta = \frac{ab-ac+bc-ab+ac-bc}{\sqrt{a^2+b^2+c^2}\sqrt{(b-c)^2+(c-a)^2+(a-b)^2}}\) \(\cos \theta = \frac{0}{\sqrt{a^2+b^2+c^2}\sqrt{(b-c)^2+(c-a)^2+(a-b)^2}} = 0\)…
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