JEE Main 2022 · 29 June · Evening Shift · Mathematics · Definite Integration
If ∫02(2x−2x−x2)dx={∫}_{0}^{2}\left(\sqrt{2x} - \sqrt{2x - {x}^{2}}\right)dx =∫02(2x−2x−x2)dx=
∫01(1−1−y2−y22)dy+∫12(2−y22)dy+I{∫}_{0}^{1}\left(1 - \sqrt{1 - {y}^{2}} - \dfrac{{y}^{2}}{2}\right)dy + {∫}_{1}^{2}\left(2 - \dfrac{{y}^{2}}{2}\right)dy + I∫01(1−1−y2−2y2)dy+∫12(2−2y2)dy+I, then III equal to
C. ∫01(1−1−y2)dy{∫}_{0}^{1}\left(1 - \sqrt{1 - {y}^{2}}\right)dy∫01(1−1−y2)dy
Given,
∫02(2x−2x−x2)dx={∫}_{0}^{2}\left(\sqrt{2x} - \sqrt{2x - {x}^{2}}\right)dx =∫02(2x−2x−x2)dx=
∫01(1−1−y2−y22)dy+∫12(2−y22)dy+I{∫}_{0}^{1}\left(1 - \sqrt{1 - {y}^{2}} - \dfrac{{y}^{2}}{2}\right)dy + {∫}_{1}^{2}\left(2 - \dfrac{{y}^{2}}{2}\right)dy + I∫01(1−1−y2−2y2)dy+∫12(2−2y2)dy+I
Solving LHS =∫02(2x−2x−x2)dx=83−π2= {∫}_{0}^{2}\left(\sqrt{2x} - \sqrt{2x - {x}^{2}}\right)dx = \dfrac{8}{3} - \dfrac{\pi}{2}=∫02(2x−2x−x2)dx=38−2π
Now, solving RHS =∫01(1−1−y2−y22)dy+∫12(2−y22)dy+I= {∫}_{0}^{1}\left(1 - \sqrt{1 - {y}^{2}} - \dfrac{{y}^{2}}{2}\right)dy + {∫}_{1}^{2}\left(2 - \dfrac{{y}^{2}}{2}\right)dy + I=∫01(1−1−y2−2y2)dy+∫12(2−2y2)dy+I
=I+53−π4= I + \dfrac{5}{3} - \dfrac{\pi}{4}=I+35−4π
Now equating LHS and RHS we get, I=1−π4=∫01(1−1−y2)dyI = 1 - \dfrac{\pi}{4} = {∫}_{0}^{1}\left(1 - \sqrt{1 - {y}^{2}}\right)dyI=1−4π=∫01(1−1−y2)dy as ∫01(1−y2)dy=π4{∫}_{0}^{1}\left(\sqrt{1 - {y}^{2}}\right)dy = \dfrac{\pi}{4}∫01(1−y2)dy=4π