MCQ

Direction cosines of the line passing through the points A (- 4, 2, 3) and B (1, 3, -2) are.........

#### Options

`+-1/sqrt51,+-5/sqrt51,+-1/sqrt51`

`+-5/sqrt51, +-1/sqrt51, +- (-5)/sqrt51`

`+-sqrt5,+-1,+-5`

`+-sqrt51,+-sqrt51+-sqrt51`

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#### Solution

The direction ratios of the line are 1 + 4, 3 − 2, −2 − 3 i.e., 5, 1, −5

∴ the direction cosines of the line are

`+-5/sqrt(5^2+1^2+(-5)^2), +-1/sqrt(5^2+1^2+(-5)^2), +- -5/sqrt(5^2+1^2+(-5)^2)`

i.e `+-5/sqrt51, +-1/sqrt51, +- -5/sqrt51`

Concept: Direction Cosines and Direction Ratios of a Line

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