sqrt() - New CSS functional notation (#21154)

* `sqrt()` - New CSS functional notation

* Add browser-compat

* Markdown lint

* Update files/en-us/web/css/sqrt/index.md

Co-authored-by: wbamberg <will@bootbonnet.ca>

* Update index.md

Co-authored-by: wbamberg <will@bootbonnet.ca>

files/en-us/web/css/sqrt/index.md

@@ -0,0 +1,64 @@
+---
+title: sqrt()
+slug: Web/CSS/sqrt
+page-type: css-function
+tags:
+  - CSS
+  - CSS Function
+  - Function
+  - Layout
+  - Reference
+  - Web
+  - sqrt
+  - Experimental
+browser-compat: css.types.sqrt
+---
+
+{{CSSRef}}{{SeeCompatTable}}
+
+The **`sqrt()`** [CSS](/en-US/docs/Web/CSS) [function](/en-US/docs/Web/CSS/CSS_Functions) is an exponential function that returns the [square root](https://en.wikipedia.org/wiki/Square_root) of a number.
+
+The function `pow(x, 0.5)` is equivalent to `sqrt(x)`.
+
+## Syntax
+
+```css
+/* A <number> value */
+width: calc(100px * sqrt(9));   /*  300px */
+width: calc(100px * sqrt(25));  /*  500px */
+width: calc(100px * sqrt(100)); /* 1000px */
+```
+
+### Parameters
+
+The `sqrt(x)` function accepts only one value as its parameter.
+
+- `x`
+  - : A calculation which resolves to a {{cssxref("&lt;number&gt;")}} greater than or equal to 0.
+
+### Return value
+
+Returns a {{cssxref("&lt;number&gt;")}} which is the square root of `x`.
+
+- if `x` is `+∞`, the result is `+∞`.
+- If `x` is `0⁻`, the result is `0⁻`.
+- If `x` is less than `0`, the result is `NaN`.
+
+### Formal syntax
+
+{{CSSSyntax}}
+
+## Specifications
+
+{{Specifications}}
+
+## Browser compatibility
+
+{{Compat}}
+
+## See also
+
+- {{CSSxRef("pow")}}
+- {{CSSxRef("hypot")}}
+- {{CSSxRef("log")}}
+- {{CSSxRef("exp")}}