\emph{Using Henstock's generalized Riemann integral, we show that, for anyalmost surely non-negative random variable $X$ with probability densityfunction $f_{X}$ and survival function $s_{X}(x):=\int_{x}^{\infty}f_{X}(t)dt$, the expected value of $X$ is given by $\mathbf{E}%(X)=\int_{0}^{\infty }s_{X}(x)dx$.}
@article{178, title = {The Darth Vader Rule}, journal = {Tatra Mountains Mathematical Publications}, volume = {51}, year = {2012}, doi = {10.2478/tatra.v52i0.178}, language = {EN}, url = {http://dml.mathdoc.fr/item/178} }
Muldowney, Pat; Ostaszewski, Krzysztof; Wojdowski, Wojciech. The Darth Vader Rule. Tatra Mountains Mathematical Publications, Tome 51 (2012) . doi : 10.2478/tatra.v52i0.178. http://gdmltest.u-ga.fr/item/178/