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KCET · Maths · Definite Integration

\(\int_0^1 \log \left(\frac{1}{x}-1\right) d x\) is

  1. A \(1\)
  2. B \(0\)
  3. C \(\log _2 2\)
  4. D \(\log _e\left(\frac{1}{2}\right)\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(0\)

Step-by-step Solution

Detailed explanation

\(\begin{aligned} & \int_0^1 \log \left(\frac{1}{x}-1\right) d x=\int_0^1 \log \left(\frac{1-x}{x}\right) d x \\ & I=\int_0^1 \log \left(\frac{1}{1+0-x}-1\right)=\int_0^1 \log \left(\frac{1}{1-x}-1\right) d x \\ & I=\int_0^1 \log \left(\frac{1-1+x}{1-x}\right) d x=\int_0^1 \log \left(\frac{x}{1-x}\right) d x \\ & 2 I=\int_0^1\left(\log \left(\frac{1-x}{x}\right)+\log \left(\frac{x}{1-x}\right)\right) d x \\ & 2 I=0 \quad \Rightarrow I=0 .\end{aligned}\)