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Question: Answered & Verified by Expert
Let $\overrightarrow{\mathrm{a}}, \overrightarrow{\mathrm{b}}$ and $\overrightarrow{\mathrm{c}}$ be three mutually perpendicular vectors each
of unit magnitud. If $\overrightarrow{\mathrm{A}}=\overrightarrow{\mathrm{a}}+\overrightarrow{\mathrm{b}}+\overrightarrow{\mathrm{c}}, \quad \overrightarrow{\mathrm{B}}=\overrightarrow{\mathrm{a}}-\overrightarrow{\mathrm{b}}+\overrightarrow{\mathrm{c}}$ and
$\overrightarrow{\mathrm{C}}=\overrightarrow{\mathrm{a}}-\overrightarrow{\mathrm{b}}-\overrightarrow{\mathrm{c}}$, then which one of the following is correct?
MathematicsVector AlgebraNDANDA 2018 (Phase 2)
Options:
  • A $|\overrightarrow{\mathrm{A}}|>|\overrightarrow{\mathrm{B}}|>|\overrightarrow{\mathrm{C}}|$
  • B $|\overrightarrow{\mathrm{A}}|=|\overrightarrow{\mathrm{B}}| \neq|\overrightarrow{\mathrm{C}}|$
  • C $|\overrightarrow{\mathrm{A}}|=|\overrightarrow{\mathrm{B}}|=|\overrightarrow{\mathrm{C}}|$
  • D $|\overrightarrow{\mathrm{A}}| \neq|\overrightarrow{\mathrm{B}}| \neq|\overrightarrow{\mathrm{C}}|$
Solution:
1874 Upvotes Verified Answer
The correct answer is: $|\overrightarrow{\mathrm{A}}|=|\overrightarrow{\mathrm{B}}|=|\overrightarrow{\mathrm{C}}|$
For simplicity let us take $\vec{a}, \vec{b}, \vec{c}$ as $\hat{i}, \hat{j}, \hat{k}$
Now magnitude of $\overrightarrow{\mathrm{A}}, \overrightarrow{\mathrm{B}}$ and $\overrightarrow{\mathrm{C}}$ will be $\sqrt{3}$.

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