a 2 + b 2 = c 2 {\displaystyle a^{2}+b^{2}=c^{2}} d d x ( ∫ 0 x f ( u ) d u ) = f ( x ) {\displaystyle {\frac {d}{dx}}\left(\int _{0}^{x}f(u)\,du\right)=f(x)}
