intdx/(e^x+e^-x)^2=?
সঠিক উত্তরঃ
B.
-1/(2(e^(2x)+1))+c
Explanation: 
Another Explanation (5):
সমাধান:
ধরি, \(I = \int \frac{dx}{(e^x + e^{-x})^2}\)
\(I = \int \frac{dx}{(e^x + \frac{1}{e^x})^2}\)
\(I = \int \frac{dx}{(\frac{e^{2x} + 1}{e^x})^2}\)
\(I = \int \frac{e^{2x} dx}{(e^{2x} + 1)^2}\)
এখন, ধরি \(u = e^{2x} + 1\)
তাহলে, \(\frac{du}{dx} = 2e^{2x}\)
সুতরাং, \(dx = \frac{du}{2e^{2x}}\)
তাহলে, \(I = \int \frac{e^{2x}}{u^2} \cdot \frac{du}{2e^{2x}}\)
\(I = \int \frac{1}{2u^2} du\)
\(I = \frac{1}{2} \int u^{-2} du\)
\(I = \frac{1}{2} \cdot \frac{u^{-1}}{-1} + c\)
\(I = -\frac{1}{2u} + c\)
\(I = -\frac{1}{2(e^{2x} + 1)} + c\)
সুতরাং, \(\int \frac{dx}{(e^x + e^{-x})^2} = -\frac{1}{2(e^{2x} + 1)} + c\) 🎉