∫ cos ( t ) t d t = ∫ u {\displaystyle \int {\frac {\cos {({\sqrt {t}})}}{\sqrt {t}}}dt=\int {\sqrt {u}}}
u = π t d u = π d x 1 π d u = d x {\displaystyle {\begin{aligned}u&=\pi t\\[2ex]du&=\pi \;dx\\[2ex]{\frac {1}{\pi }}du&=dx\end{aligned}}}
![{\displaystyle {\begin{aligned}u&=\pi t\\[2ex]du&=\pi \;dx\\[2ex]{\frac {1}{\pi }}du&=dx\end{aligned}}}](https://en.wikipedia.org/api/rest_v1/media/math/render/svg/7c2418f4bc086aa2cd3aadb1386f8fa76256387e)