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JEE Main 202227 JulyMorning Shift
Exam
JEE Main
Year
2022
Date
27 July
Shift
Morning Shift
Subject
Mathematics
Chapter
Differential Equations

JEE Main 2022 · 27 July · Morning Shift · Mathematics · Differential Equations

Let y = y (x) be the solution curve of the differential equation (2...

Let y=yy = y\left(x\right)bethesolutioncurveofthedifferentialequation<br/>be the solution curve of the differential equation<br />\sin \left(2{x}^{2}\right)\log_{e}\left(tan{x}^{2}\right)dy + \left(4xy - 4\sqrt{2}xsin\left({x}^{2} - \dfrac{\pi}{4}\right)\right)dx = 0, 0 < x < \sqrt{\dfrac{\pi}{2}}<br/>,whichpassesthroughthepoint(π6,1)<br />, which passes through the point \left(\sqrt{\dfrac{\pi}{6}}, 1\right). Then \left|y\left(\sqrt{\dfrac{\pi}{3}}\right)\right| is equal to _______.

Correct answer

0

Step-by-step solution

Given differential equation, sin⁡(2x2)ln⁡(tanx2)dy+(4xy−42xsin(x2−π4))dx=0\sin \left(2{x}^{2}\right)\ln \left(tan{x}^{2}\right)dy + \left(4xy - 4\sqrt{2}xsin\left({x}^{2} - \dfrac{\pi}{4}\right)\right)dx = 0

⇒ln⁡(tanx2)dy+4xydxsin⁡(2x2)−42xsin(x2−π4)sin⁡(2x2)dx=0⇒ \ln \left(tan{x}^{2}\right)dy + \dfrac{4xydx}{\sin \left(2{x}^{2}\right)} - \dfrac{4\sqrt{2}xsin\left({x}^{2} - \dfrac{\pi}{4}\right)}{\sin \left(2{x}^{2}\right)}dx = 0

⇒d(y⋅ln⁡(tanx2))−42x(sinx2−cosx2)2(2sinx2cosx2)dx=0⇒ d\left(y \cdot \ln \left(tan{x}^{2}\right)\right) - 4\sqrt{2}x\dfrac{\left(sin{x}^{2} - cos{x}^{2}\right)}{\sqrt{2}\left(2sin{x}^{2}cos{x}^{2}\right)}dx = 0

⇒d(yln(tanx2))−4x(sinx2−cosx2)(sinx2+cos⁡2x)2−1dx=0⇒ d\left(yln\left(tan{x}^{2}\right)\right) - \dfrac{4x\left(sin{x}^{2} - cos{x}^{2}\right)}{{\left(sin{x}^{2} + \cos^{2}x\right)}^{2} - 1}dx = 0

Now integrating both side,

⇒∫d(yln(tanx2))−∫4x(sinx2−cosx2)(sinx2+cos⁡2x)2−1dx=∫0⇒ ∫ d\left(yln\left(tan{x}^{2}\right)\right) - ∫ \dfrac{4x\left(sin{x}^{2} - cos{x}^{2}\right)}{{\left(sin{x}^{2} + \cos^{2}x\right)}^{2} - 1}dx = ∫ 0

Now let sinx2+cos⁡2x=t⇒−2x(sinx2−cos⁡2x)=dtsin{x}^{2} + \cos^{2}x = t ⇒ - 2x\left(sin{x}^{2} - \cos^{2}x\right) = dt

⇒∫d(yln(tanx2))+2∫dtt2−1=∫0⇒ ∫ d\left(yln\left(tan{x}^{2}\right)\right) + 2 ∫ \dfrac{dt}{{t}^{2} - 1} = ∫ 0

⇒yln(tanx2)+2⋅12ln⁡∣t−1t+1∣=c⇒ yln\left(tan{x}^{2}\right) + 2 \cdot \dfrac{1}{2}\ln \left|\dfrac{t - 1}{t + 1}\right| = c

yln(tanx2)+ln⁡(sinx2+cosx2−1sinx2+cosx2+1)=cyln\left(tan{x}^{2}\right) + \ln \left(\dfrac{sin{x}^{2} + cos{x}^{2} - 1}{sin{x}^{2} + cos{x}^{2} + 1}\right) = c

Put y = 1 and x=π6x = \sqrt{\dfrac{\pi}{6}}

1ln⁡(13)+ln(12+32−1)(12+32+1)=c1\ln \left(\dfrac{1}{\sqrt{3}}\right) + ln\dfrac{\left(\dfrac{1}{2} + \dfrac{\sqrt{3}}{2} - 1\right)}{\left(\dfrac{1}{2} + \dfrac{\sqrt{3}}{2} + 1\right)} = c

Now at x=π3x = \sqrt{\dfrac{\pi}{3}}

⇒y(ln3)+ln(32+12−1)(32+12+1)=ln⁡(13)+ln⁡(3−13+3)⇒ y\left(ln\sqrt{3}\right) + ln\dfrac{\left(\dfrac{\sqrt{3}}{2} + \dfrac{1}{2} - 1\right)}{\left(\dfrac{\sqrt{3}}{2} + \dfrac{1}{2} + 1\right)} = \ln \left(\dfrac{1}{\sqrt{3}}\right) + \ln \left(\dfrac{\sqrt{3} - 1}{\sqrt{3} + 3}\right)

⇒y(ln3)=ln⁡(13)</p><p>⇒ y\left(ln\sqrt{3}\right) = \ln \left(\dfrac{1}{\sqrt{3}}\right)</p><p>⇒ y = - 1</p><p>So,∣y∣=1</p><p>So, \left|y\right| = 1

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