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The angle between the lines whose direction cosines satisfy the equations l + m + n = 0 and l² = m² + n² is

1. π/6
2. π/2
3. π/3
4. π/4

Correct answer: π/3

Solution

The given equations describe the relationship between the direction cosines of two lines. The first equation indicates that the sum of the direction cosines is zero, while the second equation relates the squares of the cosines, leading to a specific geometric interpretation that results in an angle of π/3 between the lines.

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