# 3.10.7.1.1 `<equation-block>`

Use the `<equation-block>`

element to represent an equation that
is presented as a separate block within a text flow. Block equations can be
numbered.

When an `<equation-block>`

element has multiple direct child elements,
each child represents an alternative form of the equation. Processors are free to choose the
form or forms that they use in deliverables. For example, if there is both an image and
MathML markup, an HTML-generating processor could output both the image reference and the
MathML with appropriate HTML `@class`

or `@id`

values to enable
dynamic showing or hiding of one form or the other based on browser capability.

## Content models

See appendix for information about this element in OASIS document type shells.

## Inheritance

+ topic/ ►div◄ equation-d/equation-block

## Example

In the following example, a block equation uses MathML as its content:

```
<p>A block equation using MathML:</p>
<equation-block>
<mathml>
<m:math>
<m:semantics>
<m:mrow>
<m:msqrt>
<m:mrow>
<m:msup>
<m:mi>a</m:mi>
<m:mn>2</m:mn>
</m:msup>
<m:mo>+</m:mo><m:msup>
<m:mi>b</m:mi>
<m:mn>2</m:mn>
</m:msup>
</m:mrow>
</m:msqrt>
</m:mrow>
</m:semantics>
</m:math>
</mathml>
</equation-block>
```

In the following example, a block equation uses an image as its content:

```
<p>A block equation using an image:</p>
<equation-block>
<image keyref="equation-image-01">
<alt>a squared plus b squared.</alt>
</image>
</equation-block>
```

```
<equation-block>
<image keyref="equation-image-01">
<alt>a squared plus b squared.</alt>
</image>
<mathml>
<m:math>
<m:semantics>
<m:mrow>
<m:msqrt>
<m:mrow>
<m:msup>
<m:mi>a</m:mi>
<m:mn>2</m:mn>
</m:msup>
<m:mo>+</m:mo><m:msup>
<m:mi>b</m:mi>
<m:mn>2</m:mn>
</m:msup>
</m:mrow>
</m:msqrt>
</m:mrow>
</m:semantics>
</m:math>
</mathml>
</equation-block>
```

## Attributes

The following attributes are available on this element: Universal attribute group and outputclass.