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The direction cosines of two lines are r...

The direction cosines of two lines are related by `l + m + n = 0 and al^2 + bm^2 + cn^2=0`. The linesare parallel if

A

`a+b+c=0`

B

`a^(-1)+b^(-1)+c^(-1)=0`

C

`a=b=c`

D

none of these

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The correct Answer is:
B
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