Question

What will be the cross product of the vectors 2i + 3j + k and 6i + 9j + 3k?

(a) i + 2j + k

(b) i – j – 5k

(c) 0

(d) 2i – j – 5k

This question was posed to me in a national level competition.

My doubt stems from Computational Geometry in section Computational Geometry of Data Structures & Algorithms II

Answer 1

Right answer is (c) 0

Easy explanation - The given vectors are parallel to each other. The cross product of parallel vectors is 0 because sin(0) is 0.