CBSE 2026 · Region 3 · Set 1 · Q16 · 1 mark
If $\displaystyle l_{1}, \mathrm{~m}_{1}, \mathrm{n}_{1}$ and $\displaystyle l_{2}, \mathrm{~m}_{2}, \mathrm{n}_{2}$ are direction cosines of lines $\displaystyle \mathrm{L}_{1}$ and $\displaystyle \mathrm{L}_{2}$ respectively and $\displaystyle \theta$ is the acute angle between them, then :
Official answer
From CBSE’s own marking scheme for this paper.
(D)
$\displaystyle \cos \theta=\left|l_{1} l_{2}+\mathrm{m}_{1} \mathrm{~m}_{2}+\mathrm{n}_{1} \mathrm{n}_{2}\right|$
Three Dimensional GeometryAngle between Two LinesRemembermcqeasy
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CBSE Class 12 Mathematics past-paper question from the 2026board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.