JEE Main 2021MathematicsVector AlgebraMediumMCQ

JEE Main 2021 — Vector Algebra Question with Solution

JEE Main 2021 (16 Mar Shift 1)

Question

Let a vector αi^+βj^ be obtained by rotating the vector 3i^+j^ by an angle 45° about the origin in counterclockwise direction in the first quadrant. Then the area (in sq. units) of triangle having vertices α,β,0,β and 0,0 is equal to

Choose an option

Show full solutionCorrect option: A
Correct answer
A12

Step-by-step explanation

Area of ΔOA'B=12OA'cos15°×OA'sin15°

=12OA'2sin30°2

Now, OA=OA', since rotation will not change the magnitude.

=3+1×18=12 sq. units

Practice this on the real CBT interface

Solve this JEE Main question (and the rest of the Vector Algebra chapter) on PrepSharp's TCS iON-style CBT player — with timer, bookmarks and session analytics.

Solve interactively →

About this question

This is a previous-year question from JEE Main 2021, covering the Vector Algebra chapter of Mathematics. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.