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Show that the Lines X − 5 7 = Y + 2 − 5 = Z 1 and X 1 = Y 2 = Z 3 Are Perpendicular to Each Other.

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Question

Show that the lines \[\frac{x - 5}{7} = \frac{y + 2}{- 5} = \frac{z}{1} \text{ and } \frac{x}{1} = \frac{y}{2} = \frac{z}{3}\] are perpendicular to each other.

Sum
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Solution

The direction ratios of the lines 

\[\frac{x - 5}{7} = \frac{y + 2}{- 5} = \frac{z}{1} and \frac{x}{1} = \frac{y}{2} = \frac{z}{3}\] are proportional to 7, -5, 1 and 1, 2, 3, respectively. 

Let: 

\[\overrightarrow{b_1} = 7 \hat{i} - 5 \hat{j} + \hat{k}  \]

\[ \overrightarrow{b_2} = \hat{i}  + 2 \hat{j}  + 3 \hat{k} \]

Now, 

\[\overrightarrow{b_1} . \overrightarrow{b_2} = \left( 7 \hat{i} - 5 \hat{j} + \hat{k} \right) . \left( \hat{i} + 2 \hat{j}  + 3 \hat{k}  \right)\]

\[ = 7 - 10 + 3\]

\[ = 0\]

\[ \therefore \overrightarrow{b_1} \perp \overrightarrow{b_2}\]

Hence, the given lines are perpendicular to each other.

 

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Chapter 27: Straight Line in Space - Exercise 28.2 [Page 17]

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R.D. Sharma Mathematics Volume 1 and 2 [English] Class 12
Chapter 27 Straight Line in Space
Exercise 28.2 | Q 19 | Page 17

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