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MHT CET · Maths · Definite Integration

\(
\int_{-a}^{a} x^{2}\left(\frac{e^{x^{3}}-e^{-x^{3}}}{e^{x^{3}}+e^{-x^{3}}}\right) d x=
\)

  1. A \(a^{2}\)
  2. B 0
  3. C \(a\)
  4. D \(2 \int_{0}^{a} x^{2}\left(\frac{e^{x^{3}}-e^{-x^{3}}}{e^{x^{3}}+e^{-x^{3}}}\right) d x\)
Verified Solution

Answer & Solution

Correct Answer

(B) 0

Step-by-step Solution

Detailed explanation

Let
\(f(x) =x^{2}\left[\frac{e^{x^{3}}-e^{-x^{3}}}{e^{x^{3}}+e^{-x^{3}}}\right]=x^{2}\left[\frac{e^{x^{3}}-\frac{1}{e^{x^{3}}}}{e^{x^{3}}+\frac{1}{e^{x^{3}}}}\right]=\) \(x^{2}\left[\frac{\left(e^{x^{3}}\right)^{2}-1}{\left(e^{x^{3}}\right)^{2}+1}\right] \)
\( f(-x) =(-x)^{2}\left[\frac{e^{-x^{3}}-e^{x^{3}}}{e^{-x^{3}}+e^{x^{3}}}\right]\)
\(=x^{2}\left[\frac{\frac{1}{e^{x^{3}}}-e^{x^{3}}}{\frac{1}{e^{x^{3}}}+e^{x^{3}}}\right]=x^{2}\left[\frac{1-\left(e^{x^{3}}\right)^{2}}{1+\left(e^{x^{3}}\right)^{2}}\right]=\) \(-x^{2}\left[\frac{\left(e^{x^{3}}\right)^{2}-1}{1+\left(e^{x^{3}}\right) 2}\right]=-f(x)\)
Thus \(f(-x)=-f(x) \Rightarrow\) Given function is an odd function.
\(\therefore \quad I=0\)