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TS EAMCET · Maths · Three Dimensional Geometry

The obtuse angle between the lines whose direction ratios are determined by the equations \(a+b+c=0,2 a b+2 a c-b c=0\) is

  1. A \(\frac{5 \pi}{4}\)
  2. B \(\frac{2 \pi}{3}\)
  3. C \(\frac{7 \pi}{6}\)
  4. D \(\frac{6 \pi}{5}\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(\frac{2 \pi}{3}\)

Step-by-step Solution

Detailed explanation

We have, \(a+b+c=0\) and \(2 a b+2 a c-b c=0\) \(\begin{aligned} & a=-(b+c) \\ & \therefore \quad-2(b+c) b+-2(b+c) c-b c=0 \\ & \Rightarrow \quad-2 b^2-2 b c-2 b c-2 c^2-b c=0 \\ & \end{aligned}\)…