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The value of 01[logxlog(1x)]dx\int_0^1 [\log x - \log(1-x)] dx is

Solution

Correct Option: 4

Given: 01[logxlog(1x)]dx\int_0^1 [\log x - \log(1-x)] \, dx

The integral can be split into two parts:

01[logxlog(1x)]dx=01logxdx01log(1x)dx\int_0^1 [\log x - \log(1-x)] \, dx = \int_0^1 \log x \, dx - \int_0^1 \log(1-x) \, dx


Consider the second integral: 01log(1x)dx\int_0^1 \log(1-x) \, dx

Let u=1xu = 1-x

Then du=dxdu = -dx

Change of limits:

  • When x=0x = 0, u=1u = 1
  • When x=1x = 1, u=0u = 0

Substituting:

01log(1x)dx=10logu(du)\int_0^1 \log(1-x) \, dx = \int_1^0 \log u \cdot (-du)

=10logudu= -\int_1^0 \log u \, du

=01logudu= \int_0^1 \log u \, du

=01logxdx= \int_0^1 \log x \, dx


Substituting back into the original expression:

01[logxlog(1x)]dx=01logxdx01log(1x)dx\int_0^1 [\log x - \log(1-x)] \, dx = \int_0^1 \log x \, dx - \int_0^1 \log(1-x) \, dx

=01logxdx01logxdx= \int_0^1 \log x \, dx - \int_0^1 \log x \, dx

=0= 0


Therefore, 01[logxlog(1x)]dx=0\int_0^1 [\log x - \log(1-x)] \, dx = 0

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