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Mathematics 17 Online
OpenStudy (dls):

Limits

OpenStudy (dls):

\[\LARGE \lim_{x \rightarrow 0} \frac{e^{tanx}-e^x}{tanx-x}\]

mathslover (mathslover):

LaTeX suggestion, use \tan rather than "tan" `\tan ` is better than `tan` in LaTeX \(\tan \) , \(tan\) \(\LARGE \lim_{x \rightarrow 0} \frac{e^{\tan x}-e^x}{\tan x-x} \)

OpenStudy (dls):

Okay

mathslover (mathslover):

I think it is 1.

OpenStudy (anonymous):

0/0 form appy lhospital rule

OpenStudy (dls):

L hopsital didn't work for me

OpenStudy (dls):

and @mathslover it is one

OpenStudy (anonymous):

simply series expand e^x&e^tanx

OpenStudy (dls):

\[\LARGE \frac{e^{tanx} \times \sec^2x -e^x}{\sec^2x-1}\] after differentiating

OpenStudy (dls):

still 0/0

OpenStudy (dls):

And how can i expand using series for e^tanx? it would lead me nowhere,i tried that though.

OpenStudy (dls):

@hartnn

OpenStudy (anonymous):

e^x=1+x+x^2/2!+....... e^tanx=1+tanx+(tanx)^2/2!+.....

OpenStudy (dls):

yes

OpenStudy (dls):

i don't think it will lead to the answer

mathslover (mathslover):

Differentiate both numerator and denominator.

OpenStudy (dls):

I did

OpenStudy (anonymous):

yeah

OpenStudy (dls):

\[\LARGE \frac{e^{tanx} \times \sec^2x -e^x}{\sec^2x-1}\]

OpenStudy (yrelhan4):

we have to convert it in something like (e^x-1)/x.. this is equal to 1..

mathslover (mathslover):

oops sorry, didn't scroll above. You're on right track, what you did next?

OpenStudy (anonymous):

various method to solve limit problems

hartnn (hartnn):

divide numerator and denominator by xe^x

OpenStudy (anonymous):

but LHOSPITAL EASY METHOD..............

hartnn (hartnn):

those were my first thoughts, donno whether it will work

OpenStudy (dls):

L hospital is giving 0/0

OpenStudy (dls):

@hartnn might work

mathslover (mathslover):

Yes^

OpenStudy (anonymous):

CONVERT DETEMINANT FORM

OpenStudy (yrelhan4):

differentiate again..

OpenStudy (anonymous):

DIFF AGAIN & AGAIN

OpenStudy (dls):

lol

hartnn (hartnn):

differentiate infinite times :P

OpenStudy (dls):

there should be an easy alternate method for this

mathslover (mathslover):

www.mathportal.org/calculators/calculus/limit-calculator.php?val1=(e^tan+x+-+e^x)+/+(tan+x+-x+)&val2=%5Clim%5Climits_%7Bx+%5Cto+0%7D+%7E+%5Cdfrac%7B%7B%5Cmathrm%7Be%7D%7D^%7B%5Ctan%5Cleft(x%5Cright)%7D-%7B%5Cmathrm%7Be%7D%7D^%7Bx%7D%7D%7B%5Ctan%5Cleft(x%5Cright)-x%7D&val3=0&rb1=both even wolframs says the same but does NOT describe the answer.

mathslover (mathslover):

Hmm, I think I got it. Wait

OpenStudy (dls):

i told already it is one

mathslover (mathslover):

Here it is. \( \large {\lim _ {x \rightarrow 0 } \cfrac{e^{\tan x} - e^x}{\tan x - x} \\ \textbf{By taking e^x common from numerator and then using : } \\ \ \lim _ {x \rightarrow 0 } {f(x). g(x)} = \lim _ {x \rightarrow 0} * \lim _{ x\rightarrow 0} g(x) \\ \implies 1 ( \lim_ {x\rightarrow 0}\cfrac{e^{\tan x - x} -1}{\tan x -x} )\\ \textbf{Put tan x - x = y} : \\ \qquad \\ \lim _ {y\rightarrow 0} \cfrac{e^y - 1}{y} = 1 }\)

mathslover (mathslover):

Sorry it took time for me to write it all. I am little bit tired now a days :)

mathslover (mathslover):

Hope it helps @DLS

hartnn (hartnn):

just one note, as x-> 0 tan x-x ->0 and hence y->0 then you can apply that standard limit.

OpenStudy (anonymous):

e^tanx-e^x/tanx-x= e^tanx[ 1- e^x/e^tanx]/ tanx-x = e^tanx[ 1- e^x-tanx]/tanx-x = e^ tanx[ 1- e^ -(tanx-x)]/tanx-x further apply rule

OpenStudy (anonymous):

DLS UNDERSTAND U

OpenStudy (anonymous):

FINALLY ANS 1

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