Single Choice

Consider the line
$$\displaystyle {L}_{1}:\dfrac{{x}+1}{3}=\dfrac{{y}+2}{1}=\dfrac{{z}+1}{2},\ \displaystyle {L}_{2}:\dfrac{{x}-2}{1}=\dfrac{{y}+2}{2}=\dfrac{{z}-3}{3}$$
The shortest distance between $$L_1$$ and $$L_2$$ is
B$$\displaystyle \dfrac{17}{\sqrt{3}}$$
Correct Answer
C$$\displaystyle \dfrac{41}{5\sqrt{3}}$$
Correct Answer
D$$\displaystyle \dfrac{17}{5\sqrt{3}}$$
Correct Answer
Solution
$${ L }_{ 1 }:\cfrac { x+1 }{ 3 } =\cfrac { y+2 }{ 1 } =\cfrac { z+1 }{ 2 } $$
$$ { L }_{ 2 }:\cfrac { x-2 }{ 1 } =\cfrac { y+2 }{ 2 } =\cfrac { z-3 }{ 3 } $$
$$ (x_{ 1 },y_{ 1 },z_{ 1 })\equiv (-1,-2,-1)$$
$$ (x_{ 2 },y_{ 2 },z_{ 2 })\equiv (2,-2,3)$$
$$ (l_{ 1 },m_{ 1 },n_{ 1 })\equiv (3,1,2)$$
$$ (l_{ 2 },m_{ 2 },n_{ 2 })\equiv (1,2,3)$$
$$\vec { { b }_{ 1 } } ={ l }_{ 1 }\hat { i } +{ m }_{ 1 }\hat { j } +{ n }_{ 1 }\hat { k } $$
$$ \vec { { b }_{ 2 } } ={ l }_{ 2 }\hat { i } +{ m }_{ 2 }\hat { j } +{ n }_{ 2 }\hat { k } $$
$$\therefore $$ Shortest distance$$=(\vec { a_{ 2 } } -\vec { { a }_{ 1 } } )\cdot \cfrac { \vec { { b }_{ 1 } } \times \vec { { b }_{ 2 } } }{ |\vec { { b }_{ 1 } } \times \vec { { b }_{ 2 } } | } $$
$$\cfrac { \begin{bmatrix} x_{ 2 }-x_{ 1 } & y_{ 2 }-y_{ 1 } & z_{ 2 }-z_{ 1 } \\ l_{ 1 } & m_{ 1 } & n_{ 1 } \\ l_{ 2 } & m_{ 2 } & n_{ 2 } \end{bmatrix} }{ \sqrt { (m_{ 1 }n_{ 2 }-n_{ 1 }m_{ 2 })^{ 2 }+(m_{ 2 }l_{ 1 }-l_{ 2 }m_{ 1 })^{ 2 }+(n_{ 1 }l_{ 2 }-l_{ 1 }n_{ 2 })^{ 2 } } } $$
$$=\cfrac { 17 }{ 5\sqrt { 3 } } units$$
3D Geometry
If the shortest distance between the lines $$\displaystyle \frac{x-1}{\alpha} = \frac{y+1}{-1} = \frac{z}{1}, \,\,\, (\alpha \neq -1)$$ and
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3D Geometry
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3D Geometry
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3D Geometry
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