alleryTwo lines are parallel if their direction ratios are:
APerpendicular
BProportional (a₁/a₂ = b₁/b₂ = c₁/c₂)
CRandom
DEqual
Answer & Solution
Correct answer: B. Proportional (a₁/a₂ = b₁/b₂ = c₁/c₂)
Two lines parallel iff their direction ratios are proportional.
Two lines perpendicular iff dot product of direction vectors = 0: a₁a₂ + b₁b₂ + c₁c₂ = 0.
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