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QJEEM24Ma5849: JEE Main 2024 Mathematics - Class 12 JEEM24Ma5849 Solution: If , where is the integration constant, then is equal to

If ∫sin⁡32x+cos⁡32xsin⁡3xcos⁡3xsin⁡(x−θ)dx=Acos⁡θtan⁡x−sin⁡θ+Bcos⁡θ−sin⁡θcot⁡x+C\int \frac{\sin ^{\frac{3}{2}} x+\cos ^{\frac{3}{2}} x}{\sqrt{\sin ^3 x \cos ^3 x \sin (x-\theta)}} d x=A \sqrt{\cos \theta \tan x-\sin \theta}+B \sqrt{\cos \theta-\sin \theta \cot x}+C , where CC is the integration constant, then ABA B is equal to

Multiple Choice Options

  • A 2sec⁡θ2 \sec \theta
  • B 8cosec⁡(2θ)8 \operatorname{cosec}(2 \theta)
  • C 4cosec⁡(2θ)4 \operatorname{cosec}(2 \theta)
  • D 4sec⁡θ4 \sec \theta

Step-by-Step Verified Solution

amp;∫sin⁡32x+cos⁡32xsin⁡3xcos⁡3xsin⁡(x−θ)dxamp;I=∫sin⁡32x+cos⁡32xsin⁡3xcos⁡3x(sin⁡xcos⁡θ−cos⁡xsin⁡θ)dxamp;=∫sin⁡32xsin⁡32xcos⁡2xtan⁡xcos⁡θ−sin⁡θdx+∫cos⁡32xsin⁡2xcos⁡32xcos⁡θ−cot⁡xsin⁡θdx=amp;∫sec⁡2xtan⁡xcos⁡θ−sin⁡θdx+∫cosec⁡2xcos⁡θ−cot⁡xsin⁡θdxamp;\begin{aligned}& \text {} \int \frac{\sin ^{\frac{3}{2}} x+\cos ^{\frac{3}{2}} x}{\sqrt{\sin ^3 x \cos ^3 x \sin (x-\theta)}} d x \\& I=\int \frac{\sin ^{\frac{3}{2}} x+\cos ^{\frac{3}{2}} x}{\sqrt{\sin ^3 x \cos ^3 x(\sin x \cos \theta-\cos x \sin \theta)}} d x \\& =\int \frac{\sin ^{\frac{3}{2}} x}{\sin ^{\frac{3}{2}} x \cos ^2 x \sqrt{\tan x \cos \theta-\sin \theta}} d x+\int \frac{\cos ^{\frac{3}{2}} x}{\sin ^2 x \cos ^{\frac{3}{2}} x \sqrt{\cos \theta-\cot x \sin \theta}} d x= \\& \int \frac{\sec ^2 x}{\sqrt{\tan x \cos \theta-\sin \theta}} d x+\int \frac{\operatorname{cosec}^2 x}{\sqrt{\cos \theta-\cot x \sin \theta}} d x \\&\end{aligned}

I=I1+I2\mathrm{I}=\mathrm{I}_1+\mathrm{I}_2 ...... {Let}

For I1\mathrm{I}_1 , let tan⁡xcos⁡θ−sin⁡θ=t2\tan \mathrm{x} \cos \theta-\sin \theta=\mathrm{t}^2

sec⁡2xdx=2tdtcos⁡θ\sec ^2 x d x=\frac{2 t d t}{\cos \theta}

For I2\mathrm{I}_2 , let cos⁡θ−cot⁡xsin⁡θ=z2\cos \theta-\cot \mathrm{x} \sin \theta=\mathrm{z}^2

cosec⁡2xdx=2zdzsin⁡θ\operatorname{cosec}^2 x d x=\frac{2 z d z}{\sin \theta}

amp;I=I1+I2amp;=∫2tdtcos⁡θt+∫2zdzsin⁡θzamp;=2tcos⁡θ+2zsin⁡θamp;=2sec⁡θtan⁡xcos⁡θ−sin⁡θ+2cosec⁡θcos⁡θ−cot⁡xsin⁡θamp; Comparing amp;AB=8cosec⁡2θ\begin{aligned}& I=I_1+I_2 \\& =\int \frac{2 t d t}{\cos \theta t}+\int \frac{2 z d z}{\sin \theta z} \\& =\frac{2 t}{\cos \theta}+\frac{2 z}{\sin \theta} \\& =2 \sec \theta \sqrt{\tan x \cos \theta-\sin \theta}+2 \operatorname{cosec} \theta \sqrt{\cos \theta-\cot x \sin \theta} \\& \text { Comparing } \\& \quad A B=8 \operatorname{cosec} 2 \theta\end{aligned}

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