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Let fk(x)=1/k(sin^k x+cos^k x) Then f4(x...

Let `f_k(x)=1/k(sin^k x+cos^k x)` Then `f_4(x)-f_6(x)` =

A

`1/6`

B

`1/3`

C

`1/4`

D

`1/12`

Text Solution

Verified by Experts

The correct Answer is:
D

`f_4(x) -f_6(x) =1/4(sin^4x+cos^4x)-1/6(sin^6+cos^6x)`
`=(3(sin^4x+cos^4x)-2(sin^6+cos^6x))/12`
`=(3(1-2sin^2cos^2x)-2(1-3sin^2xcos^2x))/12`
`1/12`
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