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#1 2008-01-25 09:08:00

tony123
Member
Registered: 2007-08-03
Posts: 189

Evaluate Integral

Evaluate Integral

Last edited by tony123 (2008-01-25 09:08:58)

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#2 2008-01-25 09:18:43

JaneFairfax
Member
Registered: 2007-02-23
Posts: 6,868

Re: Evaluate Integral

Krizalid, ¿dónde estás? tongue


Q: Who wrote the novels Mrs Dalloway and To the Lighthouse?

A: Click here for answer.

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#3 2008-01-25 13:38:50

Krizalid
Member
Registered: 2007-03-09
Posts: 51

Re: Evaluate Integral

Hola, jaja

Ya está resuelta en aquél foro. (I'm not gonna post the URL for not makin' SPAM.)

Tony: you should be patient, post your problems in one forum first, if you see that it's not solved, try with another ones.

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#4 2008-02-05 11:39:16

munnaiit
Member
Registered: 2008-02-05
Posts: 0

Re: Evaluate Integral

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#5 2008-04-30 11:51:58

moxiuming
Member
Registered: 2008-04-20
Posts: 7

Re: Evaluate Integral

let sinx=t for all x in [0,pi/2],then we got cosx=sqrt(1-x^2).so,(sinx)^25/[(sinx)^25+(cosx)^25]=t^25/[t^25+(\sqrt (1-x^2))]25=f(t).we can get the extreme values of f(t) as follows:
1.find f'(t);
2.find t such that f'(t)=0;for example t1,t2;
3.f(t1),f(t2) is the maxium and inum
4.estimate the integral by the extreme value.

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#6 2008-10-11 03:03:50

sce1912
Member
Registered: 2008-10-08
Posts: 5

Re: Evaluate Integral

The 25's look scary but it isn't actually that difficult to show that

Proof:

Let


Using the substitution

we have


Adding gives




Hence
:)
Interestingly, this method is independant of the powers of sin and cos
so for all real n

Last edited by sce1912 (2008-10-11 03:26:51)

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