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Some FP2 Help Please [MEI]

TimetoSucceed

I completely do not understand part i) and ii). How did they draw that conclusion? Im completely lost.

Reply 1

BabyMaths

Part i) Have you written out a few terms of C+iS?

Part ii) Double angle formulae.

Reply 2

TimetoSucceed

for part i I have, 1 + (n1)e^jtheta + (n2)e^2jtheta etc

Reply 3

BabyMaths

and

e^{2 i \theta}=(e^{i \theta})^2

so you have

1+\binom{n}{1}e^{i\theta}+\binom{n}{2}(e^{i \theta})^2+...

Reply 4

TimetoSucceed

Original post by BabyMaths

and

e^{2 i \theta}=(e^{i \theta})^2

so you have

1+\binom{n}{1}e^{i\theta}+\binom{n}{2}(e^{i \theta})^2+...

ahh, im not sure how that becomes (i+e^jtheta)^n though =/

Reply 5

BabyMaths

Original post by TimetoSucceed

ahh, im not sure how that becomes (1+e^jtheta)^n though =/

Expand

(1+e^{i \theta})^n

then.

It should become clear.

Reply 6

TimetoSucceed

If you expand that wouldn't you just get 1+e^jntheta, im finding this very difficult

Reply 7

TimetoSucceed

maybe the (n 1), (n 2) part is confusing me, ive always been quite confused on questions like these =/

Reply 8

BabyMaths

Original post by TimetoSucceed

If you expand that wouldn't you just get 1+e^jntheta, im finding this very difficult

No. You should review the binomial expansion.

Reply 9

davros

Original post by TimetoSucceed

If you expand that wouldn't you just get 1+e^jntheta, im finding this very difficult

No - what does the binomial theorem tell you about the expansion of

(1+z)^n

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Some FP2 Help Please [MEI]

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