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By using the properties of the definite integral, evaluate the integral: ∫0π2 cos5 xdxsin5x+cos5x - Mathematics

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प्रश्न

By using the properties of the definite integral, evaluate the integral:

`int_0^(pi/2)  (cos^5  xdx)/(sin^5 x + cos^5 x)`

योग

उत्तर

Let `I = int_0^(pi/2) (cos^5 x)/ (sin^5 x + cos ^5 x)  dx`     ....(i)

Also, `I = int_0^(pi/2) (cos^5 (pi/2 - x))/(sin^5 (pi/2 - x) + cos^5 (pi/2 - x)) dx`

`[∵ int_0^a f (x) dx = int_0^a f (a - x) dx]`

`= int_0^(pi/2) (sin^5 x)/ (cos^5x + sin^5 x)  dx`           ....(ii)

Adding (i) and (ii), we have

`2 I = int_0^(pi/2) (cos^5x)/(cos^5x + sin^5 x)  dx + int_0^(pi/2) (sin^5x)/ (cos^5 x + sin^5 x)  dx`

`= int_0^(pi/2) (cos^5 x + sin^5 x)/ (cos^5 x + sin^5 x) dx`

`= int_0^(pi/2) 1 dx = [x]_0^(pi/2) = pi/2`

Hence, `I = pi/4`

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अध्याय 7: Integrals - Exercise 7.11 [पृष्ठ ३४७]

APPEARS IN

एनसीईआरटी Mathematics [English] Class 12
अध्याय 7 Integrals
Exercise 7.11 | Q 4 | पृष्ठ ३४७

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