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If r⃗=a1⃗+λb1⃗\vec{r} = \vec{a_1} + \lambda\vec{b_1} and r⃗=a2⃗+μb2⃗\vec{r} = \vec{a_2} + \mu\vec{b_2} are two skew lines such that b1⃗×b2⃗=2i^+3j^+2k^\vec{b_1} \times \vec{b_2} = 2\hat{i}+3\hat{j}+2\hat{k}, a1⃗=i^+j^+k^\vec{a_1} = \hat{i}+\hat{j}+\hat{k} and a2⃗=2i^+3j^+k^\vec{a_2} = 2\hat{i}+3\hat{j}+\hat{k}, then the shortest distance between the lines is

Solution

✅ Correct Option: 2

Shortest distance =∣(a2⃗−a1⃗)⋅(b1⃗×b2⃗)∣∣b1⃗×b2⃗∣=\frac{|(\vec{a_2}-\vec{a_1})\cdot(\vec{b_1}\times\vec{b_2})|}{|\vec{b_1}\times\vec{b_2}|}. Here a2⃗−a1⃗=i^+2j^\vec{a_2}-\vec{a_1}=\hat i+2\hat j, whose dot product with 2i^+3j^+2k^2\hat i+3\hat j+2\hat k is 8, and ∣b1⃗×b2⃗∣=17|\vec{b_1}\times\vec{b_2}|=\sqrt{17}. So the distance is 817\frac{8}{\sqrt{17}}.

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