NDA 2021 Maths · Mathematics · Vector Algebra · medium

A vector perpendicular to both hat i+hat j and hat j+hat k is

Single correct option

A vector perpendicular to both

\hat i+\hat j

and

\hat j+\hat k

Show answer and solution

Answer: (A) $\hat i-\hat j+\hat k$

A vector perpendicular to both is parallel to their cross product

(\hat i+\hat j)\times(\hat j+\hat k)=\hat i-\hat j+\hat k

. Check dot products:

1-1+0=0

and

0-1+1=0

. The other options each fail at least one dot-product test.

Original question written in the NDA 2021 Maths pattern and checked twice for the correct answer. Not an official question paper. How we write and check questions · Corrections policy · Report a mistake