Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Vectors

Question:
Which one of the following is not true?
Options:
\(|\vec{a}|=|\vec{b}|\Rightarrow \vec{a}=\vec{b}\)
\(|\vec{a}\times \vec{b}|=(\vec{a})^2(\vec{b})^2-(\vec{a}\cdot \vec{b})^2\)
\(\vec{a}\times (\vec{b}\cdot \vec{c})\) is not defined
If the adjacent sides of a parallelogram are represented by the vectors \(\vec{a}\) and \(\vec{b}\) respectively, then its area is \(|\vec{a}\times \vec{b}|\)
Correct Answer:
\(|\vec{a}|=|\vec{b}|\Rightarrow \vec{a}=\vec{b}\)
Explanation:
Counterexample for \(a\): Let \(\vec{a}=\hat{i}+2\hat{j},\vec{b}=\hat{j}-2\hat{k}\) then \(|\vec{a}|=\sqrt{5},|\vec{b}=\sqrt{5}\) but \(\vec{a}\neq \vec{b}\)