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

Qualification => Subject Doubts => GCE AS & A2 Level => Sciences => Topic started by: AndrewCedric on May 21, 2010, 12:38:45 pm

Title: MATHS P 3 HELP MJ 08
Post by: AndrewCedric on May 21, 2010, 12:38:45 pm

Number 5 part 2
How do you get 1/4???

http://www.srepapmaxeeeerf.org/A%20Level/Maths/CIE/2008%20Jun/9709_s08_qp_3.pdf

Title: Re: MATHS P 3 HELP MJ 08
Post by: Twinkle Charms on May 21, 2010, 07:05:08 pm

1/z=1/(2costheta+i(1-2sintheta))
1/(z+2-i)=1/[2costheta+i(1-2sintheta)+2-i]
            =1/[(2costheta+2)+i(1-2sintheta-1)]
            =1/[2(1+costheta)+i(-2sintheta)]
            =1/[2(1+costheta-isintheta) * conjugate of the denominator/conjugate of the denominator


solve this ull reach to
1+costheta/[4(1+costheta) + isintheta/4(1+costheta) = 1/4 + i sintheta/4(1+costheta)


therfore real part is 1/4 which is a constant...

get it? if u have problem with the conjugation do tell...           

Title: Re: MATHS P 3 HELP MJ 08
Post by: AndrewCedric on May 22, 2010, 03:10:20 am

THANKS A LOT !!!!!!!!!!

Yea no more problems.
At first, I omitted the i in the denominator cause i think it wont be needed for the answer.
So i guess, you have to just plug all of them in and
finally simplify the Real part at the end only..

THANKS AGAIN !!!!!
Good Luck for Stats and Maths P3 if you're taking those !! :D :D :D :D :D

Title: Re: MATHS P 3 HELP MJ 08
Post by: Twinkle Charms on May 22, 2010, 08:38:46 am

yea im taking those as well Thank You =)