ln [ x → 0 lim ( x 1 ∫ 0 x ( e 2 t cos ( 3 t ) + e 3 t sinh ( 2 t ) ) 1 / t d t ) ]
Evaluate the above expression.
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The title of the question cracked me up :D ...I think it's supposed to convey that the question has nearly everything thrown in...Right?
Nice solution! Having ln outside of the limit confused me a bit, but then it struck me.
In the mean time I was wondering the application of kitchen :p
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If there were a "kitchen sink" function I'd have thrown that into the problem as well. :)
Why the kitchen sink when you can just go to the hospital?
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First look at the limit. Letting the integral be F ( x ) and f ( x ) = x , we have both of these functions going to 0 as x → 0 , and thus we have a limit of the indeterminate form 0 0 . As both functions satisfy the conditions required to apply L'Hopital's rule, we apply this rule (and use the Fundamental Theorem of Calculus) to find that our limit is equal to
S = lim x → 0 ( e 2 x cos ( 3 x ) + e 3 x sinh ( 2 x ) ) x 1 ,
which is now of the indeterminate form 1 ∞ . So now we need to look at what happens to ln ( S ) in the limit as x → 0 . We then end up with
lim x → 0 ln ( S ) = lim x → 0 x ln ( e 2 x cos ( 3 x ) + e 3 x sinh ( 2 x ) ) ,
which is of the indeterminate form 0 0 , so apply L'Hopital's to get
lim x → 0 e 2 x cos ( 3 x ) + e 3 x sinh ( 2 x ) 2 e 2 x cos ( 3 x ) − 3 e 2 x sin ( 3 x ) + 3 e 3 x sinh ( 2 x ) + 2 e 3 x cosh ( 2 x ) = 4 .
But since we must take the natural log anyway we just have 4 as our final answer.