If I n = ∫ 0 π 2 x n sin x d x , where n > 1 , then

If In=0π2xnsinxdx, where n>1, then
  1. In+nn-1In-2=nπ2n-1
  2. In-nn-1In-2=nπ2n
  3. In-nn-1In-2=-nπ2n
  4. none of the above.

Solution

We have,

In=0π2xnsinxdx

In=-xncosx0π2+0π2nxn-1cosxdx

In=n0π2xn-1cosxdx

In=nxn-1sinx0π2-0π2n-1xn-2sinxdx

In=nπ2n-1-n-1In-2

Hence,

In+nn-1In-2=nπ2n-1

Asked in: MHT CET Full Test 13

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