I'm missing something here (Integration q) (1 Viewer)

[Dumsum]

Integral of (secx)^3 . tanx

Looks so simple, probably is, simple stuff is always harder though

 

[FinalFantasy]

let I=Integral of (secx)^3 . tanx
let u=sec²x and dv\dx=secxtanx
du\dx=2sec²xtanx and v=sec x
I=sec³x-2int.sec³xtanx dx
I=sec³x-2I
therefore I=sec³x\3

 

[Sirius Black]

let I=Integral of (secx)^3 . tanx
let u=sec²x and dv\dx=secxtanx
du\dx=2sec²xtanx and v=sec x
I=sec³x-2int.sec³xtanx dx
I=sec³x-2I
therefore I=sec³x\3

I=sec³x\3+c

 

[Dumsum]

let I=Integral of (secx)^3 . tanx
let u=sec²x and dv\dx=secxtanx
du\dx=2sec²xtanx and v=sec x
I=sec³x-2int.sec³xtanx dx
I=sec³x-2I
therefore I=sec³x\3

*nods and smiles*...
We've just started Integration, is this some funky method we learn later on?

 

[shafqat]

its just reverse chain rule mate

 

[FinalFantasy]

*nods and smiles*...
We've just started Integration, is this some funky method we learn later on?

it's called integration by parts, there's probably other ways but i juz saw dat one so i used it

 

[Ogden_Nash]

you could probably do it by inspection, noticing that the derivative of secx is secxtanx

 

[Dumsum]

you could probably do it by inspection, noticing that the derivative of secx is secxtanx

Ohh, thanks This I didn't know... :S

 

[KFunk]

you could probably do it by inspection, noticing that the derivative of secx is secxtanx

∫ sec³x.tanx dx
= ∫ u² du where u = secx hence du/dx = secx.tanx
=u³/3 +c
=sec³x/3 +c

 

[nit]

Originally posted by shafqat

its just reverse chain rule mate

Haha, now that sounds very much like a Penderism.

 

[FinalFantasy]

Haha, now that sounds very much like a Penderism.

what's a "Penderism"? r u referring to Bill? lol

 

[nit]

yep, Bill Pender who I had in years 7,11 and 12

 

[shafqat]

yup
same here

 

[FinalFantasy]

wow, u both SGS 99.95 doing Med lol... i want too!
btw how many of u SGS ppl do med dat u know?

 

[~ ReNcH ~]

yep, Bill Pender who I had in years 7,11 and 12

I take it Bill Pender is a good teacher
He's a uni professor though isn't he?

 

[FinalFantasy]

I take it Bill Pender is a good teacher
He's a uni professor though isn't he?

isn't Bill the head maths teacher in SGS?

 

[nit]

Bill Pender is indeed the head of Maths at SGS. He is a great teacher - he is able to adapt his level of teaching based on his class + he makes you work during classes by constantly choosing people at random to answer questions+ he's always encouraging + he sets a mean end-of-topic class test