SOLUTION: What is the number of distinct solution of the equation {{{z^2+abs(z)}}} = {{{0}}} ?

Algebra ->  Complex Numbers Imaginary Numbers Solvers and Lesson  -> Lesson -> SOLUTION: What is the number of distinct solution of the equation {{{z^2+abs(z)}}} = {{{0}}} ?      Log On


   



Question 1076735: What is the number of distinct solution of the equation z%5E2%2Babs%28z%29 = 0 ?
Answer by ikleyn(52784) About Me  (Show Source):
You can put this solution on YOUR website!
.
What is the number of distinct solution of the equation z%5E2%2Babs%28z%29 = 0 ?
~~~~~~~~~~~~~~~~~~~~~

Let us write the number z in Trigonometry form: z = r%2A%28cos%28a%29+%2B+i%2Asin%28a%29%29.

Then z%5E2 = r%5E2%2A%28cos%282a%29%2Bi%2Asin%282a%29%29, and your equation is

r%5E2%2A%28cos%282a%29%2Bi%2Asin%282a%29%29+%2B+r = 0,   or, which is the same,

r%2A%28r%2A%28cos%282a%29+%2B+i%2Asin%282a%29%29+%2B+1%29 = 0.


The last equation deploys in two independent equations


1)  r = 0,   which means simply  z = 0.


2)  (r*(cos(2a) + i*sin(2a)) + 1 = 0,  which is the same as

    r*(cos(2a) + i*sin(2a) = -1.


    The last equation implies 

    r = 1,  cos(2a) = -1 and sin(2a) = 0,   which, in turn, implies

    r = 1  and  {2a = pi   OR  2a = 3%2Api }.

    
    It means  that the solutions are  

           a) r = 1,  a = pi%2F2,     OR/AND

           b) r = 1,  a = 3pi%2F2.


    In the rectangular form these solutions are  z = i   OR/AND  z = -i.


Answer.  The original equation has three solutions: z = 0;  z = i,  and  z = -i.


There is a bunch of lessons on complex numbers
    - Complex numbers and arithmetical operations on them
    - Complex plane
    - Addition and subtraction of complex numbers in complex plane
    - Multiplication and division of complex numbers in complex plane
    - Raising a complex number to an integer power
    - How to take a root of a complex number
    - Solution of the quadratic equation with real coefficients on complex domain

    - Solved problems on taking roots of complex numbers
    - Solved problems on arithmetic operations on complex numbers
    - Miscellaneous problems on complex numbers
    - Advanced problem on complex numbers
    - A curious example of an equation in complex numbers which HAS NO a solution
in this site.

Also, you have this free of charge online textbook in ALGEBRA-II in this site
    - ALGEBRA-II - YOUR ONLINE TEXTBOOK.

The referred lessons are the part of this online textbook under the topic "Complex numbers".