On Example 1 in this following PDF: http://home.iitk.ac.in/~psraj/mth101/lecture_notes/lecture15-16.pdf
Consider the function $f : [0, 1] \to \mathbb R$ defined by $f(1/2) = 1$ and $f(x) = 0$ for all $x \in [0, 1] \setminus \{1/2\}$
I am trying to accumulate alot of different answered questions in real analysis so that I can start to become more familiar with proofs. I found this PDF today which seems like a pretty good overview (since we are covering integration in class) but on the sheet he says that "For any partition $P$ of $[a,b]$, the $L(f,P)$ is $0$". How do we know this?