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QJEEM24Maf7b9: JEE Main 2024 Mathematics - Class 12 JEEM24Maf7b9 Solution: Let be the solution of the differential equation satisfying the …

Let y=y(x)y=y(x) be the solution of the differential equation dydx=(tan⁡x)+ysin⁡x(sec⁡x−sin⁡xtan⁡x),x∈(0,π2)\frac{d y}{d x}=\frac{(\tan x)+y}{\sin x(\sec x-\sin x \tan x)}, x \in\left(0, \frac{\pi}{2}\right) satisfying the condition y(π4)=2y\left(\frac{\pi}{4}\right)=2 . Then, y(π3)y\left(\frac{\pi}{3}\right) is

Multiple Choice Options

  • A 3(2+log⁡e3)\sqrt{3}\left(2+\log _e 3\right)
  • B 3(1+2log⁡e3)\sqrt{3}\left(1+2 \log _e 3\right)
  • C 3(2+log⁡e3)\sqrt{3}\left(2+\log _e \sqrt{3}\right)
  • D 32(2+log⁡e3)\frac{\sqrt{3}}{2}\left(2+\log _e 3\right)

Step-by-Step Verified Solution

amp;dydx=sin⁡x+ycos⁡xsin⁡x⋅cos⁡x(1cos⁡x−sin⁡x⋅sin⁡xcos⁡x)amp;=sin⁡x+ycos⁡xsin⁡x(1−sin⁡2x)amp;dydx=sec⁡2x+y⋅2(cosec⁡2x)amp;dydx−2cosec⁡(2x)⋅y=sec⁡2xamp;dydx+p⋅y=Q\begin{aligned}& \frac{d y}{d x}=\frac{\sin x+y \cos x}{\sin x \cdot \cos x\left(\frac{1}{\cos x}-\sin x \cdot \frac{\sin x}{\cos x}\right)} \\& =\frac{\sin x+y \cos x}{\sin x\left(1-\sin ^2 x\right)} \\& \frac{d y}{d x}=\sec ^2 x+y \cdot 2(\operatorname{cosec} 2 x) \\& \frac{d y}{d x}-2 \operatorname{cosec}(2 x) \cdot y=\sec ^2 x \\& \frac{d y}{d x}+p \cdot y=Q\end{aligned}

 I.F. =e∫pdx=e∫−2cosec⁡(2x)dx\text { I.F. }=\mathrm{e}^{\int p \mathrm{dx}}=\mathrm{e}^{\int-2 \operatorname{cosec}(2 \mathrm{x}) \mathrm{dx}}

Let 2x=t2 \mathrm{x}=\mathrm{t}

2dxdt=12 \frac{\mathrm{dx}}{\mathrm{dt}}=1

dx=dt2\mathrm{dx}=\frac{\mathrm{dt}}{2}

=e−∫cosec⁡(t)dt=\mathrm{e}^{-\int \operatorname{cosec}(\mathrm{t}) \mathrm{dt}}

=e−ln⁡∣tan⁡t2∣=\mathrm{e}^{-\ln \left|\tan \frac{t}{2}\right|}

=e−ln⁡∣tan⁡x∣=1∣tan⁡x∣=\mathrm{e}^{-\ln |\tan x|}=\frac{1}{|\tan x|}

amp;y( IF )=∫Q(IF)dx+camp;⇒y1∣tan⁡x∣=∫sec⁡2x⋅1∣tan⁡x∣+camp;y⋅1∣tan⁡x∣=∫dt∣t∣+c for tan⁡x=tamp;y⋅1∣tan⁡x∣=ln⁡∣t∣+camp;y=∣tan⁡x∣(ln⁡∣tan⁡x∣+c)amp; Put x=π4,y=2amp;2=ln⁡1+c⇒c=2amp;y=∣tan⁡x∣(ln⁡∣tan⁡x∣+2)amp;y(π3)=3(ln⁡3+2)\begin{aligned}& y(\text { IF })=\int Q(I F) d x+c \\& \Rightarrow y \frac{1}{|\tan x|}=\int \sec ^2 x \cdot \frac{1}{|\tan x|}+c \\& y \cdot \frac{1}{|\tan x|}=\int \frac{d t}{|t|}+c \quad \text { for } \tan x=t \\& y \cdot \frac{1}{|\tan x|}=\ln |t|+c \\& y=|\tan x|(\ln |\tan x|+c) \\& \text { Put } x=\frac{\pi}{4}, y=2 \\& 2=\ln 1+c \Rightarrow c=2 \\& y=|\tan x|(\ln |\tan x|+2) \\& y\left(\frac{\pi}{3}\right)=\sqrt{3}(\ln \sqrt{3}+2)\end{aligned}

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