MHB How can i integrate this function

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The discussion focuses on integrating the function \[ \int_{0}^{\inf} \frac{e^{-\frac{(x-a)^2}{b}}}{x^2-c^2} dx\] using the residue theorem. Participants suggest rewriting the function as a complex variable and integrating along the real axis, considering the semicircular path in the complex plane. It is noted that if b and c are real, the integration path must loop around the poles at b and c on the real line. Calculating the integral over small semicircles around these poles is essential for accurate results. The application of the residue theorem is emphasized as a potential method for solving the integral.
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\[ \int_{0}^{\inf} \frac{e^{-\frac{(x-a)^2}{b}}}{x^2-c^2} dx\] or \[ \int_{0}^{constant} \frac{e^{-\frac{(x-a)^2}{b}}}{x^2-c^2} dx\]

maybe application Residue theorem integral ? because this problem same the kramers kronig relation?
 
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The "residue theorem" applies to functions of a complex variable. Are you planning to rewrite the function as a function of a complex variable, with path of integration the x-axis from x- R to x+ R and the semicircle $z= R \cos(\theta)+ iR \sin(\theta)4$ and then take R going to infinity?

If b and c are real numbers then you path will need to loop around b and c on the real line. Whether your loops include b and c or not you will need to calculate the integral over those small semi-circles.
 
There are probably loads of proofs of this online, but I do not want to cheat. Here is my attempt: Convexity says that $$f(\lambda a + (1-\lambda)b) \leq \lambda f(a) + (1-\lambda) f(b)$$ $$f(b + \lambda(a-b)) \leq f(b) + \lambda (f(a) - f(b))$$ We know from the intermediate value theorem that there exists a ##c \in (b,a)## such that $$\frac{f(a) - f(b)}{a-b} = f'(c).$$ Hence $$f(b + \lambda(a-b)) \leq f(b) + \lambda (a - b) f'(c))$$ $$\frac{f(b + \lambda(a-b)) - f(b)}{\lambda(a-b)}...

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