Question:medium
If the straight line passing through the points $(1,-1,2)$ and $(3,2,8)$ makes angle $\beta$ with the $y$-axis, then the value of $\cos \beta$ is equal to
If the straight line passing through the points $(1,-1,2)$ and $(3,2,8)$ makes angle $\beta$ with the $y$-axis, then the value of $\cos \beta$ is equal to
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The triplet (2, 3, 6) is very common in 3D problems because $2^2 + 3^2 + 6^2 = 49$, which is a perfect square ($7^2$). Memorizing this can speed up your calculations.
Updated On: Jun 24, 2026
- $\frac{1}{7}$
- $\frac{3}{7}$
- $\frac{2}{7}$
- $\frac{4}{7}$
- $\frac{5}{7}$
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The Correct Option is B
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