# Taylor series for getting different formulas

by ericm1234
Tags: formulas, series, taylor
 P: 67 I am trying to establish why, I'm assuming one uses taylor series, $\frac{\partial u}{\partial t}$(t+k/2, x)= (u(t+k,x)-u(t,x))/k + O(k^2) I have tried every possible combination of adding/subtracting taylor series, but either I can not get it exactly or my O(k^2) term doesn't work out (it's O(k^1) or O(k^3) )