$$ \lim\limits_{n \rightarrow \infty}\left[\frac{1}{n^2} \sec ^2 \frac{1}{n^2}+\frac{2}{n^2} \sec ^2 \frac{4}{n^2}+\ldots \ldots+\frac{1}{n} \sec ^2 1\right]= $$

$$ \int\limits_2^5 \sqrt{\frac{5-x}{x-2}} d x= $$

$$ \int\limits_0^{\frac{\pi}{2}} \sin ^6 x \cos ^4 x d x= $$