Standard Limits

$f\left(x\right)=\left\{\begin{array}{cl}\frac{{72}^x-9^x-8^x+1}{\sqrt{2}-\sqrt{1+\cos x}},& x\ne 0\\ k\log 2\log 3,& x=0\end{array}\right.$

Find the value of $\text{'}k\text{'}$ for which the function $f$ is continuous.