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Let OA⃗=2i^−j^+k^\vec{OA} = 2\hat{i} - \hat{j} + \hat{k} and OB⃗=i^+j^−k^\vec{OB} = \hat{i} + \hat{j} - \hat{k}. Then

A. The magnitude of vector OA⃗\vec{OA} is 6

B. The magnitude of vector OB⃗\vec{OB} is 3\sqrt{3}

C. The vector AB⃗\vec{AB} is (−i^+2j^−2k^)(-\hat{i} + 2\hat{j} - 2\hat{k})

D. OA⃗⋅OB⃗=0\vec{OA} \cdot \vec{OB} = 0

E. OA⃗∥OB⃗\vec{OA} \parallel \vec{OB}

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 4

∣OA⃗∣=4+1+1=6|\vec{OA}| = \sqrt{4+1+1} = \sqrt{6} (A is false).

∣OB⃗∣=3|\vec{OB}| = \sqrt{3} (B true).

AB⃗=OB⃗−OA⃗=−i^+2j^−2k^\vec{AB} = \vec{OB} - \vec{OA} = -\hat{i} + 2\hat{j} - 2\hat{k} (C true).

OA⃗⋅OB⃗=2−1−1=0\vec{OA} \cdot \vec{OB} = 2 - 1 - 1 = 0 (D true).

Since dot product is zero, vectors are perpendicular not parallel (E false).

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