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Ask iit jee aieee pet cbse icse state board community Community Discussion Question: functions problem CBSE
Forum Index -> Differential Calculus like the article? email it to a friend.  
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[Post New]14 Dec 2007 19:42:15 IST
    Subject: functions problem CBSE
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chaudhary1990 (0)

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if f(1)=4
f'(1)=2
then what is the value of derivative of logf(ex)?
What is the value at x=0?
    
[Post New]14 Dec 2007 19:51:35 IST
    Subject: Re:functions problem CBSE
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nadeemoidu (1184)

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Use the chain rule.

d [ log f( e x  ) ] /dx = 1/ f( ex )  d [ f(ex )] / dx

=[ 1/ f( ex )]  f '(ex) d [ ex ] / dx


=[ 1/ f( ex ) ] f '(ex)  ex

At x=0 , ex =1
So substitute the value of f(1) and f '(1)

=(1/4) x 2 x 1

=1/2
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