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Help:MathML guide

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MathML is an XML based system that uses tags to help a website correctly format complicated equations. This page is a guide to the basic elements of MathML for writing equations. Equations in PetroWiki can also be rendered as images (most currently are shown as images).


A tag is used to help the website correctly format an equation. Tags are surrounded by angle brackets <> to denote the fact that they will not appear in the website text. An example of a simple MathML tag is <mi>, which denotes that the next letter in the sequence will be an identifier, generally a variable like “x.” Tags almost always come in pairs and surround each element of the equation. For example, a simple variable, x, would be written as <mi>x</mi>. The end tag has a forward slash to denote that it is the end of the expression.


Tags are often stacked inside each other, for example <mrow><mi>x</mi></mrow> . This is known as nesting. Nesting is used when multiple tags apply to a single number or variable, or if a tag applies to a large number of numbers or variables. Every equation will have some elements of nesting in it.

Commonly Used Tags

Beginning Ending Used For
<code> </code> This tag begins and ends every equation.
<math> </math> This tag is nested inside the <code> tag. It is required in every equation.
<mrow> </mrow> This tag groups elements in a horizontal row.
<mi> </mi> This tag denotes an indicator, such as a variable.
<mn> </mn> This tag denotes a number.
<mo> </mo> This tag denotes an operator, such as a +, -, =, etc.
<mtext> </mtext> This tag denotes text within an equation.
<msub> </msub> This tag attaches a subscript to a base.
<msup> </msup> This tag attaches a superscript to a base.
<msubsup> </msubsup> This tag attaches a subscript and superscript to a base.
<msqrt> </msqrt> This tag forms a square root around an element or elements.
<mspace/> This tag is used as a spacer between elements

Examples of MathML Code and Explanations

Basic Equation:


As with all equations, this one begins and ends with the <code> and <math> tags. Each element of the equation is correctly tagged as a number <mn>, indicator <mi>, or operator <mo>. A space tag <mspace/> has been included between each element and the operators to help spread out the equation a little, so it is easier to read.

Equations with Superscripts:


Superscripts use the <msup> tag to identify both a base and an exponent. The base is listed first, the exponent second, and both use the appropriate tags, nested inside the <msup> tag.

Equations with Square Roots: </nowiki>

The square root tag <msqrt> puts any element of an equation that is nested inside it under the square root symbol.

More Complicated Equations

This page gives a very basic overview of how to use MathML, but MathML is a powerful tool that can produce very complex equations. The internet is full of guides and tutorials to help produce more complicated equations using MathML.

Helpful Links

The following links are a few tutorials and guides that might be helpful to you when working with MathML.