# Imaginary numbers In mathematics, the notion of number has been extended over the centuries to include zero, negative numbers, rational numbers (such as $$\frac{1}{2}$$), real numbers (such as $$\sqrt{2}$$ and $$\pi$$) and complex numbers, which extend the real numbers by introducing imaginary numbers (an imaginary number consists of the real part and the imaginary part; a common imaginary number, $$i$$, is defined as the square root of minus one, $$i = \sqrt{-1}$$). --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://mandober.gitbook.io/math-debrief/501-number-theory/617-number-sets/imaginary-numbers.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.