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If a⃗=i^−2j^+3k^\vec{a} = \hat{i} - 2\hat{j} + 3\hat{k} and b⃗=i^+2j^+k^\vec{b} = \hat{i} + 2\hat{j} + \hat{k}, then which of the following statements are correct?

(A) a⃗\vec{a} and b⃗\vec{b} are perpendicular to each other.

(B) a⃗\vec{a} and b⃗\vec{b} are parallel.

(C) ∣a⃗×b⃗∣=221|\vec{a}\times\vec{b}| = 2\sqrt{21}.

(D) Projection of a⃗\vec{a} on b⃗\vec{b} = 0.

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 3

a⃗⋅b⃗=1−4+3=0\vec{a}\cdot\vec{b}=1-4+3=0, so the vectors are perpendicular and the projection of a⃗\vec{a} on b⃗\vec{b} is 0. Hence (A) and (D) are true and (B) is false.

Since θ=90∘\theta=90^\circ, ∣a⃗×b⃗∣=∣a⃗∣∣b⃗∣=146=84=221|\vec{a}\times\vec{b}|=|\vec{a}||\vec{b}|=\sqrt{14}\sqrt6=\sqrt{84}=2\sqrt{21}, so (C) is true.

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