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NCERT Class XII Mathematics Chapter - - Solutions

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Exercise - 7.2
Integrate the functions in Exercises 23 to 59.
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Question : 41 of 271
Marks: +1, -0
e2x−1e2x+1\frac{e^{2x}-1}{e^{2x}+1}
Solution:  
Let I=∫e2x−1e2x+1dxI=\int\frac{e^{2x}-1}{e^{2x}+1}dx
=∫ex(ex−e−x)ex(ex+e−x)dx=\int\frac{e^x(e^x-e^{-x})}{e^x(e^x+e^{-x})}dx
=∫ex−e−xex+e−xdx=\int\frac{e^x-e^{-x}}{e^x+e^{-x}}dx
Put ex+e−x=te^{x} + e^{-x} = t ⇒(ex−e−x)dx=dt\Rightarrow (e^{x} - e^{-x}) dx = dt
∴I=∫dtt=log⁡∣t∣+C\therefore I=\int\frac{dt}{t}=\log|t|+C =log⁡∣ex+e−x∣+C=\log |e^{x} + e^{-x}|+C
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