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Cartesian Equations of a Line Ab Are 2 X − 1 2 = 4 − Y 7 = Z + 1 2 . Write the Direction Ratios of a Line Parallel to Ab.

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Question

Cartesian equations of a line AB are  \[\frac{2x - 1}{2} = \frac{4 - y}{7} = \frac{z + 1}{2} .\]   Write the direction ratios of a line parallel to AB.

Short/Brief Note
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Solution

We have , 

\[\frac{2x - 1}{2} = \frac{4 - y}{7} = \frac{z + 1}{2}\]

The equation of the line AB can be re-written as  ,

\[\frac{x - \frac{1}{2}}{1} = \frac{y - 4}{- 7} = \frac{z + 1}{2}\]

The direction ratios of the line parallel to AB are proportional to 1, -7, 2 .

Also, the direction cosines of the line parallel to AB are proportional to 

\[\frac{1}{\sqrt{1^2 + \left( - 7 \right)^2 + 2^2}}, \frac{- 7}{\sqrt{1^2 + \left( - 7 \right)^2 + 2^2}}, \frac{2}{\sqrt{1^2 + \left( - 7 \right)^2 + 2^2}} \]

\[ = \frac{1}{\sqrt{54}}, \frac{- 7}{\sqrt{54}}, \frac{2}{\sqrt{54}}\]

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Chapter 27: Straight Line in Space - Very Short Answers [Page 41]

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R.D. Sharma Mathematics Volume 1 and 2 [English] Class 12
Chapter 27 Straight Line in Space
Very Short Answers | Q 5 | Page 41

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