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For the vector a⃗=13(2i^−2j^+k^)\vec a = \dfrac{1}{3}(2\hat i - 2\hat j + \hat k), which of the following statements is/are TRUE ?

A. vector a⃗\vec a is a unit vector

B. vector a⃗\vec a is making an angle π3\dfrac{\pi}{3} with vector 2i^−4j^+3k^2\hat i - 4\hat j + 3\hat k

C. vector a⃗\vec a is parallel to vector −i^+j^−12k^-\hat i + \hat j - \dfrac{1}{2}\hat k

D. vector a⃗\vec a is perpendicular to vector 3i^+2j^−2k^3\hat i + 2\hat j - 2\hat k

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 1

∣a⃗∣=134+4+1=1|\vec a|=\frac{1}{3}\sqrt{4+4+1}=1, so A holds. Also −i^+j^−12k^=−12(2i^−2j^+k^)-\hat i+\hat j-\frac{1}{2}\hat k=-\frac{1}{2}(2\hat i-2\hat j+\hat k), a scalar multiple, so C holds. The dot product with 3i^+2j^−2k^3\hat i+2\hat j-2\hat k is 13(6−4−2)=0\frac{1}{3}(6-4-2)=0, so D holds. For B, cos⁡θ=529≠12\cos\theta=\frac{5}{\sqrt{29}} \neq \frac{1}{2}.

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