JEE Main 2021 · MathsNumerical answerNumerical valueHardMulti-step

JEE Main 25 February 2021, Shift 1, Maths Q81

Question 81 of 90 in this shift, Maths question 21 of 30, Section B.

\mathrm{A} = \begin{bmatrix} 0 & -\tan\left(\frac{\theta}{2}\right) \\ \tan\left(\frac{\theta}{2}\right) & 0 \end{bmatrix}

and

(\mathrm{I}_2 + \mathrm{A})(\mathrm{I}_2 - \mathrm{A})^{-1} = \begin{bmatrix} \mathrm{a} & -\mathrm{b} \\ \mathrm{b} & \mathrm{a} \end{bmatrix}

, then

13(\mathrm{a}^2 + \mathrm{b}^2)

is equal to ____________.

Official answer

NTA final key.

Chapter: Matrices
Topic: Matrix Inverse
Idea tested: Inverse of Skew-Symmetric Matrices

Same topic in other shifts

All Matrix Inverse questions

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Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.