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Consider two vectors overrightarrow u=3 i- j and overrightarrow v=2 i+ j-λ k, λ gt 0. The angle between them is given by cos ^-1 ( √5 2 √7 ). Let…

JEE Main 2025 — Mathematics Vectors & 3D Geometry

2025mcqmedium

Consider two vectors u→=3i^−j^\overrightarrow{\mathrm{u}}=3 \hat{\mathrm{i}}-\hat{\mathrm{j}}u=3i^−j^​ and v→=2i^+j^−λk^,λ>0\overrightarrow{\mathrm{v}}=2 \hat{\mathrm{i}}+\hat{\mathrm{j}}-\lambda \hat{\mathrm{k}}, \lambda \gt 0v=2i^+j^​−λk^,λ>0. The angle between them is given by cos⁡−1(527)\cos ^{-1}\left(\frac{\sqrt{5}}{2 \sqrt{7}}\right)cos−1(27​5​​). Let v→=v→1+v→2\overrightarrow{\mathrm{v}}=\overrightarrow{\mathrm{v}}_1+\overrightarrow{\mathrm{v}}_2v=v1​+v2​, where v→1\overrightarrow{\mathrm{v}}_1v1​ is parallel to u→\overrightarrow{\mathrm{u}}u and v→2\overrightarrow{\mathrm{v}}_2v2​ is perpendicular to u→\overrightarrow{\mathrm{u}}u. Then the value ∣v→1∣2+∣v→2∣2\left|\overrightarrow{\mathrm{v}}_1\right|^2+\left|\overrightarrow{\mathrm{v}}_2\right|^2​v1​​2+​v2​​2 is equal to

Official previous-year question

Held on 4 Apr 2025 · Verified 6 Jul 2026.

Options

  1. A

    232\frac{23}{2}223​

  2. B

    14

  3. C

    252\frac{25}{2}225​

  4. D

    10

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