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Find the Angle Between the Following Pairs of Lines: → R = ( 4 ^ I − ^ J ) + λ ( ^ I + 2 ^ J − 2 ^ K ) and → R = ^ I − ^ J + 2 ^ K − μ ( 2 ^ I + 4 ^ J − 4 ^ K )

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प्रश्न

Find the angle between the following pair of line: 

\[\overrightarrow{r} = \left( 4 \hat{i} - \hat{j} \right) + \lambda\left( \hat{i} + 2 \hat{j} - 2 \hat{k} \right) \text{ and }\overrightarrow{r} = \hat{i} - \hat{j} + 2 \hat{k} - \mu\left( 2 \hat{i} + 4 \hat{j} - 4 \hat{k} \right)\]

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उत्तर

\[\overrightarrow{r} = \left( 4 \hat{i} - \hat{j} \right) + \lambda\left( \hat{i} + 2 \hat{j} - 2 \hat{k} \right) \text{ and }\overrightarrow{r} = \hat{i} - \hat{j} + 2 \hat{k} - \mu\left( 2 \hat{i} + 4 \hat{j} - 4 \hat{k} \right)\]

Let `vec b_1 and vec b_2 ` be vectors parallel to the given lines .

Now,

\[\overrightarrow{b_1} = \hat{i} + 2 \hat{j} - 2 \hat{k} \]

\[ \overrightarrow{b_2} = 2 \hat{i} + 4 \hat{j} - 4 \hat{k}\]

If θ  is the angle between the given lines, then

\[\cos \theta = \frac{\overrightarrow{b_1} . \overrightarrow{b_2}}{\left| \overrightarrow{b_1} \right| \left| \overrightarrow{b_2} \right|}\]

\[ = \frac{\left( \hat{i} + 2 \hat{j} - 2 \hat{k} \right) . \left( 2 \hat{i} + 4 \hat{j} - 4 \hat{k} \right)}{\sqrt{1^2 + 2^2 + \left( - 2 \right)^2} \sqrt{2^2 + 4^2 + \left( - 4 \right)^2}}\]

\[ = \frac{2 + 8 + 8}{3 \times 6}\]

\[ = 1\]

\[ \Rightarrow \theta = 0° \]

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अध्याय 27: Straight Line in Space - Exercise 28.2 [पृष्ठ १६]

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आर.डी. शर्मा Mathematics Volume 1 and 2 [English] Class 12
अध्याय 27 Straight Line in Space
Exercise 28.2 | Q 8.1 | पृष्ठ १६

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