IGCSE/GCSE/O & A Level/IB/University Student Forum

Qualification => Subject Doubts => GCE AS & A2 Level => Math => Topic started by: @d!_†oX!© on August 12, 2010, 02:17:27 pm

Title: Improper integral
Post by: @d!_†oX!© on August 12, 2010, 02:17:27 pm

Probably a very easy question..but can anyone please explain what to do if the limits given to us for integration have either inifinite or -ve infinite??
Pure maths 1
Thanks in advance..i have an exam tom..please help if you can

Title: Re: Improper integral
Post by: Alpha on August 12, 2010, 02:41:16 pm

Hm, you have to analyse what happens to the value of your integrated expression when the value of x is increasing.

Title: Re: Improper integral
Post by: Saladin on August 12, 2010, 02:44:02 pm

Please give me a question as an example.

Title: Re: Improper integral
Post by: @d!_†oX!© on August 12, 2010, 03:10:01 pm

Quote from: Engraved on August 12, 2010, 02:44:02 pm

Please give me a question as an example.

here you go..

Title: Re: Improper integral
Post by: cooldude on August 12, 2010, 03:14:19 pm

Quote from: @d!_†oX!© on August 12, 2010, 03:10:01 pm

here you go..

integrate the integrand first, we get (x^-1)/-1=-x^-1=-1/x
the limits are infinity and 1, when x tends to infinity y tends to 0, i.e. the integral tends to 0, therefore we get 0-(-1/1)=1

Title: Re: Improper integral
Post by: cooldude on August 12, 2010, 03:15:36 pm

oh yeah and just read it from the book, ull get it, and when the limits are infinity its an infinite integral

Title: Re: Improper integral
Post by: Saladin on August 12, 2010, 05:59:44 pm

Never tried one of these before.