Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Vectors

Question:
If \(|\vec{a}\times \vec{b}|^2+|\vec{a}\cdot \vec{b}|^{2}=144\) and \(|\vec{a}|=4\), then \(|\vec{b}|\) is equal to
Options:
\(12\)
\(8\)
\(4\)
\(3\)
Correct Answer:
\(3\)
Explanation:
\(\begin{aligned}|\vec{a}\times \vec{b}|^2+|\vec{a}\cdot \vec{b}|^2&=|a|^2|b|^2\\ 144&=16\cdot |\vec{b}|^{2}\\ |\vec{b}|^{2}&=9\\ |\vec{b}|&=3\end{aligned}\)