Two lines with direction cosines a1,b1,c1 and a2,b2,c2 are called parallel if-
Answer & explanation
Correct answer: option 3
We know that two lines with direction cosine a1,b1,c1 and a2,b2,c2 are called parallel if angle θ between them is equal to zero which is possible when
a1/a2 = b1/b2 = c1/c2