JEE MAIN - Mathematics (2022 - 27th July Morning Shift - No. 8)
Let $$
I=\int_{\pi / 4}^{\pi / 3}\left(\frac{8 \sin x-\sin 2 x}{x}\right) d x
$$. Then
$${\pi \over 2} < I < {{3\pi } \over 4}$$
$${\pi \over 5} < I < {{5\pi } \over {12}}$$
$${{5\pi } \over {12}} < I < {{\sqrt 2 } \over 3}\pi $$
$${{3\pi } \over 4} < I < \pi $$
Explanation
I comes out around 1.536 which is not satisfied by any given options.
$$\int\limits_{\pi /4}^{\pi /3} {{{8x - 2x} \over x}dx > I > \int\limits_{\pi /4}^{\pi /3} {{{8\sin x - 2x} \over x}dx} } $$
$${\pi \over 2} > I > \int\limits_{\pi /4}^{\pi /3} {\left( {{{8\sin x} \over x} - 2} \right)dx} $$
$${{\sin x} \over x}$$ is decreasing in $$\left( {{\pi \over 4},{\pi \over 3}} \right)$$ so it attains maximum at $$x = {\pi \over 4}$$
$$I > \int\limits_{\pi /4}^{\pi /3} {\left( {{{8\sin x/3} \over {x/3}} - 2} \right)dx} $$
$$I > \sqrt 3 - {\pi \over 6}$$
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