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 Aug14 comment Can the following be integrated? @mixedmath thanks. I can't seem to do it numerically because when integrating the whole thing (including extra functions of y and z) over x, y and z, mathematica can't figure out where the singularities are. Aug14 comment Can the following be integrated? I don't, but sometimes an integral that looks more complicated is actually simpler, and I wanted to make sure I wasn't missing something like that. Apr27 comment Can you differentiate with respect to a sum? And I'll think some more about the ordering - thank you. Apr27 comment Can you differentiate with respect to a sum? @joriki Ahh so it should be $(\delta /\delta x(\tau')) Exp[\int_0^p d\tau (x(\tau) \alpha (\tau) - y(\tau) \beta (\tau))] = \alpha (\tau') Exp[\int_0^p d\tau (x(\tau) \alpha (\tau) - y(\tau) \beta (\tau))]$ ? (But possibly with the $\alpha$ after the integral rather than before). Apr27 comment Can you differentiate with respect to a sum? @joriki since $x$ is in front of $\alpha$, I don't think it should matter that they're Grassmann numbers.. Should it? Apr27 comment Can you differentiate with respect to a sum? @joriki I used to write the same $\tau$ for all, but have been told the way I wrote it above is the correct way since when they are all tau, it looks like you're differentiating wrt the integration variable. Apr27 comment Can you differentiate with respect to a sum? And sorry, i'm not sure why I said operators! Must be a lack of sleep. I meant Grassmann numbers! Apr27 comment Can you differentiate with respect to a sum? @joriki I'm not sure what you mean by that there's no need for the Integrating variables to be different... Apr27 comment Can you differentiate with respect to a sum? @joriki thanks. I tried to simplify the problem to much I think. I've edited my question again to hopefully make it clearer. Apr26 comment Can you differentiate with respect to a sum? $a$, $b$, $\alpha$ and $\beta$ are also operators rather than just variables. Does this make any difference? Apr26 comment Can you differentiate with respect to a sum? @joriki thanks. So since what I want is to find $\alpha Exp[(5a+3b)\alpha−(3a+5b)\beta]$ (or $\alpha Exp[x\alpha−y\beta]$ is fine too), the useful meaning for me of $\partial / \partial x$ is $\partial / \partial (5a+3b)$? Apr26 comment Can you differentiate with respect to a sum? @Christian thanks for your reply .. I've edited my question a bit to clarify a few things. Is it ok to label $x=5a+3b$ and $y=3a+5b$ or like J.M. said, do I need to write $3a+5b$ in terms of $x$? Apr26 comment Can you differentiate with respect to a sum? Thanks @J.M. @Henry @Jim and @david. I've edited my question a bit to clarify that $a$ and $b$ are not dependent on $\alpha$ or $\beta$. So is it ok to label $x=5a+3b$ and $y=3a+5b$ or like J.M. said, do I need to write $3a+5b$ in terms of $x$?