# How to prove that $\int_0^{\pi} \log(|\sin t|)\,\textrm{dt} \;\;\textrm{is integrable }$

How to prove that $$\int_0^{\pi} \log(|\sin t|)\,\textrm{dt} \;\;\textrm{is integrable }$$

Any hints would be appreciated.

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## 1 Answer

Hint: It is true that $$\sin{t} \ge \frac{2}{\pi} t$$ on the interval $[0, \pi/2]$; try drawing the graph, or noting that $\sin{t}$ is concave down and we have equality at the endpoints. Now show that

$$\int_0^{\pi/2} |\ln{\frac{2}{\pi} t}| dt < \infty$$

Do something similar for the right-half of the interval.

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