maths p3 june 2007 - q8-i

[Mortal9090]

complex number u is =-1-i
u^2 = 2i
|u^2|=2
|u| = sqrt(2)

how about the argument of u and u^2?

the marksscheme says arg(u)=-3pi/4 and arg(u^2)=.5pi

what i understand is arg of u should be arctan(-1/-1) = arctan(1) which is pi/4.

thanks

 

[ahmed t]

arg(u^2) is on the positive y axis so its 90 degrees .
where as "U" if u look at it in an argand diagram it will be in the bottom left quadrant so it will be 180-theta
were theta is pi/4 so it will be 3pi/4

 

[fireman]

Its always better if you attach the question along with your confusion ,better for the helper and as well as yours

 

[Mortal9090]

Its always better if you attach the question along with your confusion ,better for the helper and as well as yours

(i) Find the modulus and argument of u and u2.

 

[ahmed t]

did u understand my explanation

 

[Mortal9090]

thank you ahmed_tee