$$ \frac{d}{dx}\left( \int_{0}^{x} f(u)\,du\right)=f(x) $$
\[ \sin A \cos B = \frac{1}{2}\left[ \sin(A-B)+\sin(A+B) \right] \]
$$ P^{2}_{н} - P^{2}_{к}=1,2687 \cdot 10^{-4}\lambda\frac{Q^{2}_{0}}{d^{5}}\rho_{0}l$$