IGCSE/GCSE/O & A Level/IB/University Student Forum

Qualification => Subject Doubts => GCE AS & A2 Level => Math => Topic started by: Priya on June 27, 2009, 10:57:16 am

Title: Please help me with this question of complex numbers
Post by: Priya 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!!

Title: Re: Please help me with this question of complex numbers
Post by: astarmathsandphysics 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

Title: Re: Please help me with this question of complex numbers
Post by: Priya 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.

Title: Re: Please help me with this question of complex numbers
Post by: astarmathsandphysics 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.

Title: Re: Please help me with this question of complex numbers
Post by: blablabla17 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

Title: Re: Please help me with this question of complex numbers
Post by: astarmathsandphysics 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