End of limits

These are some easy ones on limit...
Please explain them and help me finish limits.

Q1) \lim_{x\rightarrow 0} \frac{e-(1+x)^{1/x}}{tan x}

Q2) \lim_{x\rightarrow 0} \left(\frac{(1+x)^{1/x}}{e} \right)^{1/x}

Q3) {P{n}}= \frac{2^{3}-1}{2^{3}+1}.\frac{3^{3}-1}{3^{3}+1}.\frac{4^{3}-1}{4^{3}+1}...\frac{n^{3}-1}{n^{3}+1}

\lim_{n\rightarrow 0} P_{n}=?

Edit: Answer:- 1-e/2 2- e-1/2 3- 2/3

15 Answers

1
Che ·

for first one use this

(1+x)1/x=e^(1x ln (1+x) )

use exp of ln (1+x)

and the apply l hospital

1
Unicorn--- Extinct!! ·

So the answer will be?

1
Che ·

1) e/2

1
Unicorn--- Extinct!! ·

Yup correct..
Is there any other method...without expansion?

1
Che ·

dunno of any oder though

1
Unicorn--- Extinct!! ·

okk thanx...rest of them?

1
Che ·

for second

((1+x)1/x e)1/x = e^((1xln(1+x)-1)1x)

expan ln(1+x) and then apply l hosptital

e^(-1/2)

1
Unicorn--- Extinct!! ·

hmm...I was trying to avoid expansion.
(Got the answer using expansion)

Still looking for alternative method

Thanx Reimann

1
Che ·

and for third are u sure its summation.....i hav done a similar q but in that each term was multiplied

1
Che ·

why trying to avoid expansion......its good to use them anywhere oder than in boards

1
Che ·

for 3rd one see this

http://targetiit.com/iit-jee-forum/posts/limit-1-12939.html

1
Unicorn--- Extinct!! ·

3rd edited
:)

1
Unicorn--- Extinct!! ·

I avoid expansion coz I usually mess up at later stages.

1
Unicorn--- Extinct!! ·

Still looking for alternative solutions to Q1 and Q2

106
Asish Mahapatra ·

Q1. u can apply L-H rule but it will be very tedious ... btw i never use the exp of (1+x)1/x cant seem to remember it .. so i use LH only

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