CBSE 2024 · Region 1 · Set 1 · Q20 · 1 mark
Assertion (A) : A line in space cannot be drawn perpendicular to $\displaystyle \mathrm{x}, \mathrm{y}$ and z axes simultaneously. Reason ( $\displaystyle R$ ) : For any line making angles, $\displaystyle \alpha, \beta, \gamma$ with the positive directions of $\displaystyle \mathrm{x}, \mathrm{y}$ and $\displaystyle z$ axes respectively, $\displaystyle \cos ^{2} \alpha+\cos ^{2} \beta+\cos ^{2} \gamma=1$.
Official answer
From CBSE’s own marking scheme for this paper.
(A)
Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
Three Dimensional GeometryDirection Cosines and Direction Ratios of a LineAnalyseassertion_reasonmedium
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CBSE Class 12 Mathematics past-paper question from the 2024board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.