How do you find |5i|?

1 Answer
Jun 6, 2016

Apply the definition |a+bi|=a2+b2 to find that

|5i|=5

Explanation:

The modulus of a complex number a+bi, denoted |a+bi|, is given by

|a+bi|=a2+b2.

and is an extension of the absolute value function, which applies to reals. The latter represents the distance from the real number to 0 on the number line, and the former represents the distance of the complex number to the origin on the complex plane.

Applying this definition to our given complex number, we have:

|5i|=|0+(5)i|

=02+(5)2

=0+25

=25

=5