ATAR Notes: Forum

VCE Stuff => VCE Mathematics => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Specialist Mathematics => Topic started by: golden on September 29, 2011, 08:58:36 pm

Title: Complex Roots
Post by: golden on September 29, 2011, 08:58:36 pm

If a question asks find the roots of a complex number do we have to have our angles in between (-pi, pi]?

Title: Re: Complex Roots
Post by: Greatness on September 29, 2011, 09:02:03 pm

Yeah you would because you're using de moivre's theorem.

Title: Re: Complex Roots
Post by: paulsterio on September 29, 2011, 09:32:40 pm

You don't have to have your angle in the principle domain of -pi to pi unless the question explicitly states it, but it's "good manners" to do so, it's like rationalising the denominator or simplifying logarithms

Like I always put it between -pi and pi because i'm pedantic, i always rationalise denominators and I never write stuff like log.e(49) i would write 2log.e(7)

Title: Re: Complex Roots
Post by: tony3272 on September 29, 2011, 09:36:37 pm

Yeah, technically if the question states the argument as Arg (upper case 'a') then you must have your angles within -pi to pi. However if they use a lower case 'a', then you're not required to, and this was reiterated by Derrick Ha today.

But, like Paul, i always change my angle since i'm pedantic about it as well.