JEE Advanced Mathematics question

The direction cosines of a line passing through the origin and cutting the line at are

Answer: (A),(D)

Solution

Let the required line have direction cosines . Two conditions must hold.

**1. Angle condition.** The given line has direction cosines . The (acute) angle between lines is , so

=\ ⇒\ |l+2m-n|= .

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Question ID VK-109852