[Glossary](https://useratio.app/glossary) › Maths and statistics

# Complex number

A number with a real part and an imaginary part, written like 3 + 4i.

The imaginary unit i is the square root of −1, so the square root of a negative number is imaginary. Complex numbers appear in electronics, signal processing and physics.

## In Ratio

| You type | Ratio shows |
| --- | --- |
| `(3 + 4i) * (1 - 2i)` | 11 - 2i |
| `sqrt(-4)` | 2i |

## Related

[Syntax and examples](https://useratio.app/docs) · [All terms](https://useratio.app/glossary)

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Source: https://useratio.app/glossary/complex-number