Geometry of Complex Addition, Subtraction & Conjugation
What does addition look like on an Argand diagram?
The?addition?of complex numbers can be shown by the addition of?corresponding column vectors
Ifand, then
This can be written as
An alternative is to write?adding the respective real and imaginary parts separately
A complex numbercan be represented by the position vector
What does subtraction look like on an Argand diagram?
As with addition we can use knowledge of vectors to represent subtraction of complex numbers
If and , then
This can be written as
An alternative is to write subtracting the respective real and imaginary parts separately
What are the geometric representations of complex addition and subtraction?
Let?w?be a given complex number with?real part?a?and?imaginary part?b
Let?z?be any complex number represented on an Argand diagram
Adding w to z results in z being translated by vector
Subtracting w from z results in z being translated by vector
What is the geometric representation of complex?conjugation?
If we plot?complex conjugate?pairs on an Argand diagram, we notice the points are?reflections?of each other in the?real axis
Let?z?be any complex number represented on an Argand diagram
Complex conjugating?z?results in?z?being?reflected?in the real axis
Worked Example
Exam Tip
Read questions carefully; is it asking to plot the complex number as a point or as a vector?
Be extra careful when representing subtraction geometrically, remember that the solution will be a translation of the shorter diagonal of the parallelogram made up by the two vectors.