MCQ
If $\phi \,(x) = {\log _5}\,{\log _3}\,x;$ then $\phi '\,(e)$ is equal to
- A$ e\ log\ 5$
- B$- e\ log\ 5$
- ✓$\frac{1}{{e\,\ln \,5}}$
- D$\frac{log 5}{{e}}$
$\phi(\mathrm{x})=\log _{\mathrm{s}}\left(\frac{\ln \mathrm{x}}{\ln 3}\right)$
$\phi ({\rm{x}}) = {\log _{\rm{s}}}{\rm{lnx}} - {\log _{\rm{s}}}\ln 3$
$\phi(x)=\frac{\ln \ln x}{\ln 5}-\log _{5} \ln 3$
$\phi^{\prime}(x)=\frac{1}{\ln 5} \times \frac{1}{\ln x} \times \frac{1}{x}$
${\phi ^\prime }(e) = \frac{1}{{e\ln S}}$
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