Complex numbers needn't be so complex. A complex number is simply a single expression that contains both a real and an imaginary part. To review, the imaginary number j (i is also commonly used) is defined as the square root of negative one. Of course, the square root of negative one isn't easy to visualize, but, as it turns out, imaginary numbers are a powerful and have many applications in the real world. Electrical power, for example, has an imaginary part in a system containing inductance and/or capacitance. This is known as complex power, an example of a complex number. Here are more examples:
$ 1+j $
$ 7 + 2j $
$ e^(2j) $
