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Evaluate the following. ∫1xlogxdx - Mathematics and Statistics

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Question

Evaluate the following.

`int 1/("x" log "x")`dx

Sum

Solution

Let I = `int 1/("x" log "x")`dx

Put log x = t

∴ `1/"x" "dx" = "dt'`

∴ I = `int 1/"t"` dt = log |t| + c

∴ I = log |log x| + c

Alternate Method:

Let I = `int 1/("x" * log "x")`dx

`= int (1//"x"  "dx")/(log "x")`

∴ I = log |log x| + c      .....`[because int ("f" '("x"))/("f"("x")) "dx" = log |"f"("x")| + "c"]`

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Chapter 5: Integration - EXERCISE 5.2 [Page 123]
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