The sum of all the natural numbers for which $log_{(4-x)}(x^2 -14x + 45)$ is defined is -
$1$
$2$
$3$
$4$
$\sum\limits_{r = 1}^{89} {{{\log }_3}(\tan \,\,{r^o})} = $
If ${\log _5}a.{\log _a}x = 2,$then $x$ is equal to
If ${1 \over {{{\log }_3}\pi }} + {1 \over {{{\log }_4}\pi }} > x,$ then $x$ be
If ${\log _e}\left( {{{a + b} \over 2}} \right) = {1 \over 2}({\log _e}a + {\log _e}b)$, then relation between $a$ and $b$ will be
$\sum\limits_{n = 1}^n {{1 \over {{{\log }_{{2^n}}}(a)}}} = $