$\lim _{x \rightarrow \pi / 4} \dfrac{(\sqrt{2}-\sec x) \cos x(1+\cot x)}{\cot x\left[2-\sec ^{2} x\right]}$
$=\lim _{x \rightarrow \pi / 4} \dfrac{\sin x(1+\cot x)}{(\sqrt{2}+\sec x)}$
$=\frac{\dfrac{1}{\sqrt{2}}(2)}{\sqrt{2}+\sqrt{2}}$
$=\dfrac{1}{2}$