Page 77 - A Guide to MATLAB for Beginners and Experienced Users

58 Chapter 4: Beyond the Basics

r = sqrt(xˆ2 + yˆ2);
theta = atan2(y,x);

If you type polarcoordinates(3,4), only the first output argument is re-
turned and stored in ans; in this case, the answer is 5. To see bothoutputs,
you must assign them to variables enclosed in square brackets:
>> [r, theta] = polarcoordinates(3,4)

r=
5

theta =
0.9273
By typing r = polarcoordinates(3,4) you can assign the first output ar-
gument to the variable r, but you cannot get only the second output argument;
typing theta = polarcoordinates(3,4) will still assign the first output,
5,to theta.

Complex Arithmetic

MATLAB does most of its computations using complex numbers, that is, num-
√
bers of the form a + bi, where i = −1 and a and b are real numbers. The
complex number i is represented as i in MATLAB. Although you may never
have occasion to enter a complex number in a MATLAB session, MATLAB
often produces an answer involving a complex number. For example, many
polynomials withreal coefficients have complex roots:
>> solve(’xˆ2 + 2*x+2=0’)

ans =
[ -1+i]
[ -1-i]
Bothroots of this quadratic equation are complex numbers, expressed in
terms of the number i. Some common functions also return complex values
for certain values of the argument. For example,
>> log(-1)

ans =
0 + 3.1416i