Can Someone Integrate This?? (1 Viewer)

[JUB JUB]

xe^x^2

looks easy but i can't get the right answer....
the answer is 1/2e^x^2 ....
someone please

 

[ND]

Use a u=x^2 substitution.

 

[JUB JUB]

ahh sorry it's not working out!
can someone show me how to get the final answer?

 

[Affinity]

the way teh 2 unit teacher in our school teaches:

notice d/dx [ e^(x^2)] = 2x(e^(x^2))

(1/2)d/dx [ e^(x^2)] = x(e^(x^2))

(1/2)(e^(x^2)) is the answer.

the 'proper' way

let u=x^2

du/dx = 2x
(1/2) du = x dx

(integrate) xe^x^2 dx
= (integrate) (1/2) e^u du
= (1/2)e^u + C
= (1/2)e^(x^2)

 

[JUB JUB]

THANKKKKKKKKKSSSSSS!

thanks a lot!!!!
hope i pass !!!

G'LUCK

 

[Piper_Aviator]

Remember though...if it is an indefinite integral to add +C at the end. So it becomes 1/2e^x^2 + C.

 

[Viper]

I thought intergration using substitution was only a 3unit topic?

How do we do this using 2 unit knowledge?

Cheers

 

[Affinity]

the '3 unit method' is easier,
since the '2 unit method' requires you too see it in 1 step

 

[mercury]

using a substitution would probably enable to see it much better i suppose. It's regarded as the safe method.
IMO, Just practise heaps and you'll be able to tell when these type of stuff come around.

 

[KeypadSDM]

Originally posted by mercury
Just practise heaps and you'll be able to tell when these type of stuff come around.

Always look for the ones that look like this:

f'(x) * e ^ f(x)
f'(x) * Cos[f(x)] (or Sin)

Looking for the f'(x) out the front is they key to getting most of the supposed 'tricky' ones out quickly.

 

[Angela86]

oo I love integration. man I'm a nerd

 

[evilc]

everyone loves integration

 

[Grey Council]

everyone does? :-\

I don't. I'm trying to do 3u integration without having done the integration/differentiation of logs and trig functions. I hate it.

Bleh, my teacher stuffed me up in the year 11 yearlies, so now I absolutely SUCK at trig. ABSOLUTELY, and completely, totally suck at trig.

Guess I should fix it up sometime these holidays. :-/

 

[Angela86]

Yeah, my maths teacher sucks as well.
He seems to have this idea that putting us down motivates us.
I get so sick of his bullcrap, maths would be my fave subject if my techer stopped putting evey one down and actualy started to teach us.
All I can say is thank go for my tutoring teacher

 

[Supra]

LOL angela ur teacher is xactly like mine...and he has fukd me up on 2u probability, i did the 2u hsc in 2003, and had to fukn guess and pray my way thru the probability question in it...now im doin fukn 4u this yr, im sooooo screwed for 3u/4u probability

 

[Angela86]

I can not do probability at all, I try and try and try and it just wont click. Not even my tutorer can help me there, so they key for me is have a guess and try and pick up marks where others don't. It's been workin for me so far, I think I got 3rd or 4th in the course for our 1st assesment task.

 

[abdooooo!!!]

i don't know about you people but probability comes naturally to me... don't know why though... its proly the law of probility that leads us to being different.

 

[Angela86]

lol. Yeah I guess it's one of those things that is hard for some people and easy for others.
I can only do probability if I have a probability tree. hrmmm. And they aren't suitable for all types of probibility.

 

[Sexy_Guy]

I suggest if u cannot do probability just drop down to general or drop maths altogether because probability is the most logical sub-section of mathematics and if you cannot do it then u cannot do maths cause maths is ALL LOGIC, & i have bad news 4 u, u cannot GUESS your way through the HSC!!!!!

 

[abdooooo!!!]

Originally posted by Sexy_Guy
I suggest if u cannot do probability just drop down to general or drop maths altogether because probability is the most logical sub-section of mathematics and if you cannot do it then u cannot do maths cause maths is ALL LOGIC, & i have bad news 4 u, u cannot GUESS your way through the HSC!!!!!

you can with general... with the multi choice LOL.