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Find the Angle Between the Lines → R = ( 2 ^ I − 5 ^ J + ^ K ) + λ ( 3 ^ I + 2 ^ J + 6 ^ K ) and → R = 7 ^ I − 6 ^ K + μ ( ^ I + 2 ^ J + 2 ^ K ) - Mathematics

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प्रश्न

Find the angle between the lines 

\[\vec{r} = \left( 2 \hat{i}  - 5 \hat{j}  + \hat{k}  \right) + \lambda\left( 3 \hat{i}  + 2 \hat{j}  + 6 \hat{k}  \right)\] and \[\vec{r} = 7 \hat{i} - 6 \hat{k}  + \mu\left( \hat{i}  + 2 \hat{j}  + 2 \hat{k}  \right)\] 

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उत्तर

Let 

θ  be the angle between the given lines. The given lines are parallel to the vectors \[\overrightarrow{b_1} = 3 \hat{i} + 2 \hat{j} + 6 \hat{k} \] and 

\[\overrightarrow{b_2} = \hat{i} + 2 \hat{j} + 2 \hat{k}\]  respectively. 

So, the angle θ  between the given lines is given by 

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

\[ = \frac{\left( 3 \hat{i}  + 2 \hat{j}  + 6 \hat{k} \right) . \left( \hat{i} + 2 \hat{j} + 2 \hat{k} \right)}{\sqrt{3^2 + 2^2 + 6^2}\sqrt{1^2 + 2^2 + 2^2}}\]

\[ = \frac{3 \times 1 + 2 \times 2 + 6 \times 2}{\sqrt{49}\sqrt{9}}\]

\[ = \frac{19}{21}\]

\[ \Rightarrow \theta = \cos^{- 1} \left( \frac{19}{21} \right)\] 

Thus, the angle between the given lines is

\[\cos^{- 1} \left( \frac{19}{21} \right)\]

 

 

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अध्याय 28: Straight Line in Space - Very Short Answers [पृष्ठ ४२]

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आरडी शर्मा Mathematics [English] Class 12
अध्याय 28 Straight Line in Space
Very Short Answers | Q 20 | पृष्ठ ४२

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