Odd or Even?

Calculus Level 3

Let f ( x ) f(x) be an odd, real to real, continuous and differentiable function.
Then f ( x ) f'(x) is always a/an:

Can't say Even function Odd function

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2 solutions

Rishabh Jain
May 5, 2016

f ( x ) = f ( x ) ( f ( x ) is odd ) f(-x)=-f(x)~~(\because f(x)\text{ is odd}) Differentiating both sides we get: ( 1 ) f ( x ) = f ( x ) (-1)f'(-x)=-f'(x) f ( x ) = f ( x ) \implies f'(-x)=f'(x) which implies f ( x ) f'(x) is an Even Function .

Great! I like your solution more than mine XD

展豪 張 - 5 years, 1 month ago

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Thanks..... ¨ \ddot\smile .

Rishabh Jain - 5 years, 1 month ago
展豪 張
May 5, 2016

f ( x ) \;\;\;\;f'(-x)
= d f ( x ) d ( x ) =\dfrac{\mathrm{d}f(-x)}{\mathrm{d}(-x)}
= d f ( x ) d x =\dfrac{-\mathrm{d}f(x)}{-\mathrm{d}x} ( f ( x ) f(x) as odd function)
= d f ( x ) d x =\dfrac{\mathrm{d}f(x)}{\mathrm{d}x}
= f ( x ) =f'(x)
which meets the definition of an even function.


f(x)=3x is odd then df/d(x) =3 thats is oven also >okay nice and easy

Patience Patience - 5 years, 1 month ago

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f ( x ) = 3 x f(x)=3x is only a special case. Though this is an easy way to duel with a multiple choices question.

展豪 張 - 5 years, 1 month ago

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f(x)=a you sure its oven thats ask i am choosing uncorrect i think its not even

Patience Patience - 5 years, 1 month ago

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@Patience Patience Please don't use abbreviations/slangs as I don't understand. What is your question?

展豪 張 - 5 years, 1 month ago

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