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∫(1loget−1(loget)2)dt\int \left(\frac{1}{log_e t} - \frac{1}{(log_e t)^2}\right) dt is equal to

Solution

✅ Correct Option: 2

Given integral: ∫(1log⁡et−1(log⁡et)2)dt\int \left(\frac{1}{\log_e t} - \frac{1}{(\log_e t)^2}\right) dt

The integrand can be recognized as the derivative of tlog⁡et\frac{t}{\log_e t}.


Consider differentiating tlog⁡et\frac{t}{\log_e t} using the quotient rule.

For y=uvy = \frac{u}{v}, the derivative is dydt=v⋅dudt−u⋅dvdtv2\frac{dy}{dt} = \frac{v \cdot \frac{du}{dt} - u \cdot \frac{dv}{dt}}{v^2}

Here, u=tu = t and v=log⁡etv = \log_e t

So dudt=1\frac{du}{dt} = 1 and dvdt=1t\frac{dv}{dt} = \frac{1}{t}


ddt(tlog⁡et)=(log⁡et)(1)−(t)(1t)(log⁡et)2\frac{d}{dt}\left(\frac{t}{\log_e t}\right) = \frac{(\log_e t)(1) - (t)\left(\frac{1}{t}\right)}{(\log_e t)^2}

=log⁡et−1(log⁡et)2= \frac{\log_e t - 1}{(\log_e t)^2}

=log⁡et(log⁡et)2−1(log⁡et)2= \frac{\log_e t}{(\log_e t)^2} - \frac{1}{(\log_e t)^2}

=1log⁡et−1(log⁡et)2= \frac{1}{\log_e t} - \frac{1}{(\log_e t)^2}


This matches the given integrand exactly.

Therefore: ∫(1log⁡et−1(log⁡et)2)dt=tlog⁡et+C\int \left(\frac{1}{\log_e t} - \frac{1}{(\log_e t)^2}\right) dt = \frac{t}{\log_e t} + C

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