Limits again

Lt n→∞ Lt x→0 1/(1tan2x+2tan2x+....Ntan2x)cot2x

We had a similar problem
http://www.targetiit.com/iit-jee-forum/posts/find-the-limit-10114.html

But I'm not sure about the answer...Plz someone give a complete explanation with answer :)

2 Answers

1
kartik sondhi ·

as Lt x→0 by keeping11tan2x+2tan2x1tan3x..∞=y then Take log on both sides
log 1y= cot2xlog(tan2x+2tan2x1tan3x..∞)
then Take cot2x as 1tan2x
Now Diffrentiate on both sides As L'Hospital rule

and use the tan Expansion formula

then You will get the answer

11
Devil ·

Well, I think limit is 1.We will probably have lnk=cot2xln1, meaning k=1...

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