Author Topic: Please help me with this question of complex numbers  (Read 1270 times)

Offline Priya

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Please help me with this question of complex numbers
« on: June 27, 2009, 10:57:16 am »
I have attached the question and my answer. The modulus of u and u^2 and the argument of u is right according the mark scheme. Can you tell me what is wrong with the argument of u^2?

The answer of argument of u^2 is pi/2

I am really grateful for all the help. Thank you so much!!
« Last Edit: June 27, 2009, 11:02:06 am by Priya »

Offline astarmathsandphysics

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Re: Please help me with this question of complex numbers
« Reply #1 on: June 27, 2009, 01:24:20 pm »
I think they want the ar in the range 0 to 2pi.

So do 2pi+(-3pi/2)=pi/2

Offline Priya

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Re: Please help me with this question of complex numbers
« Reply #2 on: June 27, 2009, 06:23:49 pm »
Thank you for the help =)

Just to confirm... Since it is not stated here, should I assume that for such questions, I should give my
answer between 0 and 2pi.

Thanks again.

Offline astarmathsandphysics

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Re: Please help me with this question of complex numbers
« Reply #3 on: June 27, 2009, 06:41:34 pm »
Yes I would. Since they did not tell you to give your answe between o and 2pi, -3/2pi should get full marks too.
« Last Edit: June 27, 2009, 06:43:42 pm by astarmathsandphysics »

Offline blablabla17

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Re: Please help me with this question of complex numbers
« Reply #4 on: July 01, 2009, 09:21:18 am »
hey i just learnt it today...this morning...

my teacher asked us to rmb this formula...

( z)^n= r^N(COS N angle + i sin N angle)...

follow this formula then u will get the answer...

and i think what astar said is not right...

sorry for saying that...just follow the formula my teacher gave

Offline astarmathsandphysics

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Re: Please help me with this question of complex numbers
« Reply #5 on: July 01, 2009, 10:38:56 am »
The formula is another method. I cant post fully on this as i am abroad on a mobile phone