# How I can use a vertical bar to represent evaluation in LaTeX

by Kreizhn
Tags: evaluation, latex, represent, vertical
 P: 743 Hey guys. This might not be the right place for this, but any ideas on how I can use a vertical bar to represent evaluation in LaTeX? Example $$\displaystyle \frac{d}{dt} |_{t=0} f(t)$$ I would like the vertical bar to be the size of the differential. I've tried using \left|, \right|, \vert, etc. but nothing seems to work. Thanks a lot in advance.
 HW Helper P: 2,249 Hi Kreizhn, Is this it? $$\left. \frac{d}{dt} \right|_{t=0} f(t)$$ which is given by \left. \frac{d}{dt} \right|_{t=0} f(t) Using either \left or \right on a period means the automatic delimiter sizing takes place, but only one delimiter is shown.
 Sci Advisor HW Helper PF Gold P: 4,139 How I can use a vertical bar to represent evaluation in LaTeX \frac{d}{dt} \bigg|_{t=0} f(t) achieves a similar effect with manual sizing (by using two g's) and the unneeded \left. tag. $$\frac{d}{dt} \bigg|_{t=0} f(t)$$
 P: 23 \mathbf{M \bigg|_{x^k} \Delta x^k = -f(x^k)} $$\mathbf{M \bigg|_{x^k} \Delta x^k = -f(x^k)}$$