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Definite Integration question

2023 · 24 Jan · Shift 1 · Q43
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  5. /2023 · 24 Jan · Shift 1 · Q43

Definite Integration question

2023 · 24 Jan · Shift 1 · Q43

JEE MainMathematicsDefinite IntegrationNumerical+4 / −1
The value of 8π∫0π2(cos⁡x)2023(sin⁡x)2023+(cos⁡x)2023dx{8 \over \pi }\int\limits_0^{{\pi \over 2}} {{{{{(\cos x)}^{2023}}} \over {{{(\sin x)}^{2023}} + {{(\cos x)}^{2023}}}}dx}π8​0∫2π​​(sinx)2023+(cosx)2023(cosx)2023​dx is ‾\underline{\hspace{2cm}}​
Numerical answer
View written solutionFree

Correct answer: 2

  1. Let I=∫0π/2(cos⁡x)2023(sin⁡x)2023+(cos⁡x)2023 dx.I=\int_0^{\pi/2} \frac{(\cos x)^{2023}}{(\sin x)^{2023}+(\cos x)^{2023}}\,dx.I=∫0π/2​(sinx)2023+(cosx)2023(cosx)2023​dx.

We need to find 8πI.\frac{8}{\pi}I.π8​I.

  1. Use the standard substitution x↦π2−x.x\mapsto \frac{\pi}{2}-x.x↦2π​−x. Then sin⁡(π2−x)=cos⁡x,cos⁡(π2−x)=sin⁡x.\sin\left(\frac{\pi}{2}-x\right)=\cos x,\qquad \cos\left(\frac{\pi}{2}-x\right)=\sin x.sin(2π​−x)=cosx,cos(2π​−x)=sinx. So, I=∫0π/2(sin⁡x)2023(cos⁡x)2023+(sin⁡x)2023 dx.I=\int_0^{\pi/2} \frac{(\sin x)^{2023}}{(\cos x)^{2023}+(\sin x)^{2023}}\,dx.I=∫0π/2​(cosx)2023+(sinx)2023(sinx)2023​dx.

  2. Add the two expressions for III: 2I=∫0π/2[(cos⁡x)2023(sin⁡x)2023+(cos⁡x)2023+(sin⁡x)2023(cos⁡x)2023+(sin⁡x)2023]dx.2I=\int_0^{\pi/2}\left[\frac{(\cos x)^{2023}}{(\sin x)^{2023}+(\cos x)^{2023}}+\frac{(\sin x)^{2023}}{(\cos x)^{2023}+(\sin x)^{2023}}\right]dx.2I=∫0π/2​[(sinx)2023+(cosx)2023(cosx)2023​+(cosx)2023+(sinx)2023(sinx)2023​]dx.

Inside the bracket, (cos⁡x)2023(sin⁡x)2023+(cos⁡x)2023+(sin⁡x)2023(sin⁡x)2023+(cos⁡x)2023=1.\frac{(\cos x)^{2023}}{(\sin x)^{2023}+(\cos x)^{2023}}+\frac{(\sin x)^{2023}}{(\sin x)^{2023}+(\cos x)^{2023}}=1.(sinx)2023+(cosx)2023(cosx)2023​+(sinx)2023+(cosx)2023(sinx)2023​=1. Therefore, 2I=∫0π/21 dx=π2.2I=\int_0^{\pi/2}1\,dx=\frac\pi2.2I=∫0π/2​1dx=2π​. Hence, I=π4.I=\frac\pi4.I=4π​.

  1. Now compute the required value: 8πI=8π⋅π4=2.\frac{8}{\pi}I=\frac{8}{\pi}\cdot \frac\pi4=2.π8​I=π8​⋅4π​=2.

Therefore, the value of the given expression is 2.\boxed{2}.2​.

  1. Comparison with stored correct answer:
  • Derived answer: 222
  • Stored correct answer: 222
  • They match.
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