MCQ
If $ a$ and $ b$ are unit vectors and $a - b$ is also a unit vector, then the angle between $ a $ and $ b$ is
- A$\frac{\pi }{4}$
- ✓$\frac{\pi }{3}$
- C$\frac{\pi }{2}$
- D$\frac{{2\pi }}{3}$
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$A = \left[ {\begin{array}{*{20}{c}}
{{{10}^{30}} + 5}&{{{10}^{20}} + 4}&{{{10}^{20}} + 6}\\
{{{10}^4} + 2}&{{{10}^8} + 7}&{{{10}^{10}} + 2n}\\
{{{10}^4} + 8}&{{{10}^6} + 4}&{{{10}^{15}} + 9}
\end{array}} \right]$ ,
$n \in N$, then