If $n = 1983!$,then the value of the expression $\frac{1}{\log_2 n} + \frac{1}{\log_3 n} + \frac{1}{\log_4 n} + \dots + \frac{1}{\log_{1983} n}$ is:

Number of solution$(s)$ of the equation $\ln(1 + \sin^2 x) = 1 - \ln(5 + x^2)$ is -

What is the number of real values of the parameter $k$ for which the equation $({\log _{16}}x)^2 - {\log _{16}}x + {\log _{16}}k = 0$ has exactly one solution,given that the coefficients are real?

$e^{\left(\sec h^{-1} \frac{1}{2}+\tan h^{-1} \frac{1}{2}+\sin h^{-1} \frac{1}{2}\right)}=$

If $a, b, c$ are three distinct positive numbers different from $1$ such that $[(\log_b a)(\log_c a) - \log_a a] + [(\log_a b)(\log_c b) - \log_b b] + [(\log_a c)(\log_b c) - \log_c c] = 0$,then $abc =$

$\log (\cosh 3 + \sinh 3) + \log (\cosh 3 - \sinh 3) = $