2} + {x^4}} \RIGHT)} \right]dx\) Let us take, x2 = tDifferentiating ‘x’ with respect to ‘t’:\( \Rightarrow 2x\FRAC{{dx}}{{DT}} = 1\) ⇒ 2x dx = dt\( \Rightarrow xdx = \frac{1}{2}{\rm{\;}}dt\) Then,\( \Rightarrow I = \frac{1}{2}\mathop \smallint \limits_0^1 {\rm{\;co}}{{\rm{t}}^{ - 1}}{\rm{\;}}\left( {1 - t + {t^2}} \right)dt\) We need to convert cot x to tan x for easy calculation.\( \Rightarrow I = \frac{1}{2}\mathop \smallint \limits_0^1 {\tan ^{ - 1}}\frac{1}{{\left( {1 - t + {t^2}} \right)}}\) By using the formula,∵ \({\tan ^{ - 1}}x - {\tan ^1}y = {\tan ^{ - 1}}\left( {\frac{{x - y}}{{1 + xy}}} \right)\)In this problem, (x = t); (y = t – 1)\( \Rightarrow I = \frac{1}{2}\mathop \smallint \limits_0^1 {\tan ^{ - 1}}\left( {\frac{{t - \left( {t - 1} \right)}}{{1 + t\left( {t - 1} \right)}}} \right)dt{\rm{\;}}\) \( \Rightarrow I = \frac{1}{2}\mathop \smallint \limits_0^1 TA{n^{ - 1}}{\rm{\;}}t - ta{n^{ - 1}}\left( {t - 1} \right)dt{\rm{\;}}\) \( \Rightarrow I = \frac{1}{2}\left[ {\mathop \smallint \limits_0^1 {{\tan }^{ - 1}}{\rm{\;}}t{\rm{\;}}dt - \mathop \smallint \limits_0^1 {{\tan }^{ - 1}}\left( {t - 1} \right)dt} \right]{\rm{\;}}\) By using the formula,\(\mathop \smallint \limits_0^a f\left( x \right)dx = \mathop \smallint \limits_0^a f\left( {a - x} \right){\rm{\;}}dx\) Then, it becomes\( \Rightarrow I = \frac{1}{2}\left[ {\mathop \smallint \limits_0^1 {{\tan }^{ - 1}}{\rm{\;}}t{\rm{\;}}dt - \mathop \smallint \limits_0^1 {{\tan }^{ - 1}}\left( {1 - t - 1} \right)dt} \right]\) \( \Rightarrow I = \frac{1}{2}\left[ {\mathop \smallint \limits_0^1 {{\tan }^{ - 1}}{\rm{\;}}t{\rm{\;}}dt - \mathop \smallint \limits_0^1 {{\tan }^{ - 1}}\left( { - t} \right)dt} \right]\) \( \Rightarrow I = \frac{1}{2}\left[ {\mathop \smallint \limits_0^1 {{\tan }^{ - 1}}{\rm{\;}}t{\rm{\;}}dt + \mathop \smallint \limits_0^1 {{\tan }^{ - 1}}tdt} \right]\) ∵ tan-1 (-θ) = -tan-1 (θ)\( \Rightarrow I = \frac{1}{2}\left[ {2\mathop \smallint \limits_0^1 {{\tan }^{ - 1}}{\rm{\;}}t{\rm{\;}}dt} \right]\) \( \Rightarrow I = \mathop \smallint \limits_0^1 {\tan ^{ - 1}}{\rm{\;}}t{\rm{\;}}dt\) \( \Rightarrow I = \left[ {t.{{\tan }^{ - 1}}t - \frac{1}{2}{{\log }_e}\left( {1 + {t^2}} \right)} \right]_0^1\) \( \Rightarrow I = \left[ {t.ta{n^{ - 1}}t} \right]_0^1 - \frac{1}{2}\left[ {{{\log }_e}\left( {1 + {t^2}} \right)} \right]_0^1\) \( \Rightarrow I = \left[ {\left( {1.{{\tan }^{ - 1}}1} \right) - \left( {0.{{\tan }^{ - 1}}0} \right)} \right] - \frac{1}{2}\left[ {\left( {{{\log }_e}\left( {1 + 1} \right)} \right) - \left( {{{\log }_e}\left( {1 + 0} \right)} \right)} \right]\) \( \Rightarrow I = {\tan ^{ - 1}}1 - \frac{1}{2}{\log _e}\left( 2 \right)\) ∵ \({\tan ^{ - 1}}1 = 45^\circ = \frac{\pi }{4}\)\(\therefore I = \frac{\pi }{4} - \frac{1}{2}{\log _e}\left( 2 \right)\)