The Student Room Group

Integration question

Screenshot 2023-10-06 140236.png
Hi, I'm doing some integration questions and I need help - how should I go about doing this question? Is it integration by partial fractions? I can do all of the integration methods quite well it's just a case of choosing which one to use :redface: thanks
Original post by blizzardliz
Screenshot 2023-10-06 140236.png
Hi, I'm doing some integration questions and I need help - how should I go about doing this question? Is it integration by partial fractions? I can do all of the integration methods quite well it's just a case of choosing which one to use :redface: thanks


Its not partial fractions because the denominator, ignoring the 3 because it can be moved outside the integral, does not factorise.

To integrate 1/(1+x^2) you need a trigonometric substitution.
For the most part integration (and practically all math problems) is a case of "if the technique works, good job; if not, try something else". Key word is try (then probably try to recognize the "shape" of the integrand, so next time you know what to try first).
So say you want to try partial fractions. We want the denominator to be nicely factored, right? Well... can we do it here?

This integral, without the 1/3, is actually common enough that remembering by heart is worth it (that is, if you happen to know it).
Otherwise, as RDK suggests, it's a trig sub.
(edited 6 months ago)
Reply 3
Original post by RDKGames
Its not partial fractions because the denominator, ignoring the 3 because it can be moved outside the integral, does not factorise.

To integrate 1/(1+x^2) you need a trigonometric substitution.

Oh!!! Thank you so much
Reply 4
Original post by tonyiptony
For the most part integration (and practically all math problems) is a case of "if the technique works, good job; if not, try something else". Key word is try (then probably try to recognize the "shape" of the integrand, so next time you know what to try first).
So say you want to try partial fractions. We want the denominator to be nicely factored, right? Well... can we do it here?

This integral, without the 1/3, is actually common enough that remembering by heart is worth it (that is, if you happen to know it).
Otherwise, as RDK suggests, it's a trig sub.


I’ll try to remember it by heart, just very rusty with maths in general as I haven’t done it since my exams in June! Thank you I’ll keep that trying method in mind

Quick Reply

Latest