Example 1.2.14 (c): Multiplying geometrically

Find both geometrically and algebraically and confirm that both answers agree.
Context Context

Working algebraically with rectangular coordinates we get:


     

To work geometrically we need to find length and angle of the vectors involved:

|1/(1+i)| = 1 and Arg(1+i) = arctan(1) = /4

since 1+i and c(1+i) have the same argument for any real number c > 0. Similarly

|1/2(1+i)| = 1 and Arg(1+i) = arctan() = /3

Thus, by our theorem about dividing geometrically, we have:

= 1/1*cis(/4-/3) = cis(-/12) = 0.9659258263 - 0.2588190451 i

Therefore, both ways give the same answer.


Interactive Complex Analysis, ver. 1.0.0
(c) 2006-2007, Bert G. Wachsmuth
Page last modified: May 29, 2007