TS EAMCET · Maths · Three Dimensional Geometry
If the direction cosines of two lines are such that \(l+m+n=0, l^2+m^2-n^2=0\), then the angle between them is :
- A \(\pi\)
- B \(\pi / 3\)
- C \(\pi / 4\)
- D \(\pi / 6\)
Answer & Solution
Correct Answer
(B) \(\pi / 3\)
Step-by-step Solution
Detailed explanation
If \(l, m, n\) are direction cosines of two lines are such that \(l+m+n=0\) \(\ldots\) (i) \(l^2+m^2-n^2=0\) ...(ii) and \(l^2+m^2+n^2=1\) ...(iii) On solving Eqs. (i), (ii) and (iii), we get \(l=0, m= \pm \frac{1}{\sqrt{2}}\) and \(n= \pm \frac{1}{\sqrt{2}}\) \(\therefore\)…
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