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Question: Answered & Verified by Expert
If $(\mathbf{a} \times \mathbf{b})^2+(\mathbf{a} \cdot \mathbf{b})^2=144$ and $|\mathbf{a}|=4$, then $|\mathbf{b}|=$
MathematicsVector AlgebraJEE Main
Options:
  • A 16
  • B 8
  • C 3
  • D 12
Solution:
2043 Upvotes Verified Answer
The correct answer is: 3
We know that $(\mathbf{a} \times \mathbf{b})^2+(\mathbf{a} \cdot \mathbf{b})^2=|\mathbf{a}|^2|\mathbf{b}|^2$ $\therefore 144=16|\mathbf{b}|^2 \Rightarrow|\mathbf{b}|=3$.

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