Okay. I am trying to write down the piecewise function corresponding to the following graph...Let $r \in [0,1]$. From $0$ to $r$, I want to the function to be $y=x$; then a vertical line connecting $(r,r)$ to $(r,0)$; and then $0$ from $[r,1]$.
That middle portion is giving me trouble.
I don't know why it is giving me so much trouble...