Log-linearizing optimal price in New Keynesian model

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Homework Statement


I am going to do a log-linearization around a zero-inflation flexible price steady state of:

\frac{P_{t}^{*}}{P_{t}}E_{t}\sum_{k=0}^{\infty}\theta^{k}\beta^{k}C_{t+k}^{1-\sigma}\left(\frac{P_{t+k}}{P_{t}}\right)^{\epsilon-1}

Zero-inflation flexible price steady state implies that P_{t} = P^{*}_{t} = P_{t+k} \equiv \bar{P}.


The Attempt at a Solution



I know the solution is:
\frac{\bar{C}^{1-\sigma}}{1-\theta\beta} +\frac{\bar{C}^{1-\sigma}}{1-\theta\beta}(\hat{p}^{*}_{t} - \hat{p}_{t}) + \bar{C}^{1-\sigma}\sum_{k=0}^{\infty}\theta^{k}\beta^{k}[(1-\sigma)E_{t}\hat{c}_{t+k} + (\epsilon-1)(E_{t}\hat{p}_{t+k} - \hat{p}_{t})]

where \hat{x}_{t} = x_{t} - \bar{x}, x_{t} = \log(X_{t}), \bar{x} = \log(\bar{X}) where \bar{X} is the steady state value of X. And we have used \sum_{k=0}^{\infty}\theta^{k}\beta^{k} = \frac{1}{1-\theta\beta}.

I've now tried for several hours to do this approximation, but I just do not get to the solution. Can anyone help me on the way?
 
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It is straightforward. Please let me know if you have not figured this out yet, since your post is quite old.
Abe
 
Prove $$\int\limits_0^{\sqrt2/4}\frac{1}{\sqrt{x-x^2}}\arcsin\sqrt{\frac{(x-1)\left(x-1+x\sqrt{9-16x}\right)}{1-2x}} \, \mathrm dx = \frac{\pi^2}{8}.$$ Let $$I = \int\limits_0^{\sqrt 2 / 4}\frac{1}{\sqrt{x-x^2}}\arcsin\sqrt{\frac{(x-1)\left(x-1+x\sqrt{9-16x}\right)}{1-2x}} \, \mathrm dx. \tag{1}$$ The representation integral of ##\arcsin## is $$\arcsin u = \int\limits_{0}^{1} \frac{\mathrm dt}{\sqrt{1-t^2}}, \qquad 0 \leqslant u \leqslant 1.$$ Plugging identity above into ##(1)## with ##u...
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