## Trigonometry (10th Edition)

If $a$ and $b$ are real numbers, then any number of the form $a+bi$ is a complex number. Since $a=5$ and $b=1$ and both $a$ and $b$ are real numbers, $5+i$ is a complex number. Non-real complex numbers are complex numbers of the form $a+bi$ where $b\ne0$. Since $5+i$ fufills these prerequisites, it can be labelled as a non-real complex number as well.