this page doesn't work on mobile. hit the letter "s" to post a square to the feed. move pointer around on square to change the paramters of the curve.
$$ \left(\frac{v+f}{2}\right)\coth{\left(\frac{v+f}{2T}\right)} + \left(\frac{v-f}{2}\right)\coth{\left(\frac{v-f}{2T}\right)} $$