MCQ
Choose the correct answer from the given four options.For any two matrices A and B, we have:
- A$\text{AB}=\text{BA}$
- B$\text{AB}\neq\text{BA}$
- C$\text{AB}=\text{O}$
- ✓None of the above.
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$\left| {\begin{array}{*{20}{c}}
{{{\log }_e}\,a_1^ra_2^k}&{{{\log }_e}\,a_2^ra_3^k}&{{{\log }_e}\,a_3^ra_4^k} \\
{{{\log }_e}\,a_4^ra_5^k}&{{{\log }_e}\,a_5^ra_6^k}&{{{\log }_e}\,a_6^ra_7^k} \\
{{{\log }_e}\,a_7^ra_8^k}&{{{\log }_e}\,a_8^ra_9^k}&{{{\log }_e}\,a_9^ra_{10}^k}
\end{array}} \right| = 0$
Then the number of elements in $S$, is
$f(x)= \begin{cases}\frac{1-\cos 2 x}{x^2} & , x<0 \\ \alpha & , x=0, \text { where } \alpha, \beta \in R \text {. If } \\ \frac{\beta \sqrt{1-\cos x}}{x} & , x>0\end{cases}$
$f$ is continuous at $\mathrm{x}=0$, then $\alpha^2+\beta^2$ is equal to :