Practicing Success
\(\int_{0}^{\frac{\pi}{2}} \log \left(\sin x\right)dx\) is equal to |
\(\frac{\pi}{2}\log 2\) \(-\pi \log 2\) \(-\frac{\pi}{2}\log 2\) \(0\) |
\(-\frac{\pi}{2}\log 2\) |
\(I=\int\limits_{0}^{\frac{\pi}{2}} \log\sin xdx=\int\limits_{0}^{\frac{\pi}{2}} \log\left(\sin\left(\frac{\pi}{2}-x\right)\right)dx=\int\limits_{0}^{\frac{\pi}{2}} \log\cos xdx\) so $2I=\int\limits_{0}^{\frac{\pi}{2}} \log\sin x\cos xdx$ $2I=\int\limits_{0}^{\frac{\pi}{2}} \log\sin 2x-\log 2dx$ $2I=\frac{1}{2}\int\limits_{0}^{\pi}\log\sin xdx-\frac{\pi}{2}\log 2$ so $2I=\frac{1}{2}\int\limits_{0}^{\frac{\pi}{2}}\log\sin xdx-\frac{\pi}{2}\log 2$ $2I=I-\frac{\pi}{2}\log 2⇒I=-\frac{\pi}{2}\log 2$ |