If two lines have direction ratios (a 1 ,b 1 ,c 1 ) and (a 2 ,b 2 ,c 2 ), they are parallel if:

a 1 a 2 + b 1 b 2 + c 1 c 2 = 0

📐 Mathematics · Three Dimensional Geometry · JEE

If two lines have direction ratios (a₁,b₁,c₁) and (a₂,b₂,c₂), they are parallel if:

Answer: a₁/a₂ = b₁/b₂ = c₁/c₂.

Correct answer: B. a₁/a₂ = b₁/b₂ = c₁/c₂

Explanation: Two lines are parallel if their direction ratios are proportional: a₁/a₂ = b₁/b₂ = c₁/c₂.

Three mutually perpendicular axes x, y, z meeting at the origin O, with a point P located by its (x, y, z) coordinates.

Lines and planes in 3D space, direction cosines, distances, and angles