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#1 Re: Help Me ! » Complex Numbers » 2007-05-24 10:22:57

gairceilatan

Hi mathsyperson,

Thanks for your help, how do you decide what one to use or does it really not matter and when I done it equals to i my calculations were just off?  Or is it specific to the question?

Thank you smile

#2 Help Me ! » Complex Numbers » 2007-05-24 09:52:22

gairceilatan
Replies: 4

Hi there,

I am finding the roots of polynomials using things like, 2+i is a root of the equation hence find all the roots.

Now I am fine with these but I got a question that said the root was purely imaginary, now I took this to mean the root was just i however, this did not work out, and the answer was 2i, so my question is will a purely imaginary root for these types of questions always be 2i? 

Thank you smile

#3 Re: Help Me ! » Integration Help » 2007-05-23 07:43:00

gairceilatan

Hi JaneFairfax,

Thanks for your help can i just double check this is for secx to the power 6 (secx)^6 and not sec6x? 

I don't mean to be cheeky but your answer was not at all what I was expecting as the other questions on my sheet all involved making something = u so we could get du/dx.

Thanks again for your help big_smile

#4 Help Me ! » Integration Help » 2007-05-23 07:17:49

gairceilatan
Replies: 2

Can someone help me with this question?

∫sec^6x dx

I know that ∫sec²x dx = tanx + c but i'm stumped on this one. 

I tried making u=tanx to give du/dx=sec²x then I could not get any further.

I'm sure this is so simple you will laugh but it's driving me nuts mad

Thank you smile

#5 Re: Help Me ! » Integration » 2007-05-23 03:42:30

gairceilatan

Hi there,

Thank you everyone for your help I am sorry about not putting the whole question I like to work things out for myself, helps me remember what to do, so I thought if I could integrate cos(x²) I would have been able to solve the equation on my own.  I see now I just make the question much harder. dizzy

I live in Scotland and I only sat higher maths before going to uni which does not go as far as A-level does so this is all new to me.  Should have done the advanced higher neutral

Thanks again for all your help up

#6 Re: Help Me ! » Integration » 2007-05-22 07:48:46

gairceilatan

Hi,

I'm doing first year maths at uni and it was on a change of variable worksheet and the whole question was

∫x cos(x²) dx

I have no notes with an example like this and had no idea where to start.

Thanks for your help mathsyperson and Zhylliolom although i'm still not really sure on this at all.  I may have turned it into something harder by not putting the whole question down, however I would be grateful for any help you can give me.  smile

thank you

#7 Help Me ! » Integration » 2007-05-22 00:08:47

gairceilatan
Replies: 10

Hey,

Can someone help me with this type of question?

∫cos(x²)dx

I know how to diffrentiate it but I have no idea how to integrate it and I can't figure it out by working back the way hmm.

Many thanks

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