MathML

The Mathematical Markup Language (MathML) is a document format for representing mathematical formulas and complex expressions.

At the time of writing, only Firefox recognizes MathML inherently. To use MathML for other browsers, include the MathJax JavaScript library. MathJax is highly modular on input and output. It uses MathML, TeX, and ASCIImath as input and produces HTML+CSS, SVG, or MathML as output.
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<!DOCTYPE html><html><body style="height:200px">
<script type="text/javascript" src="https://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML"></script>
<p>Binomial Theorem:</p>

<math>
   <mrow>
      <msup>
         <mfenced>
            <mrow>
               <mi>a</mi><mo>+</mo><mi>b</mi>
            </mrow>
          </mfenced>
          <mn>2</mn>
      </msup>
      <mo>=</mo>
      <msup>
         <mrow><mi>a</mi></mrow>
         <mn>2</mn>
      </msup>
      <mo>+</mo>
      <msup>
         <mrow><mi>b</mi></mrow>
         <mn>2</mn>
      </msup>
      <mo>+</mo>
      <mrow><mn>2</mn><mi>a</mi><mi>b</mi></mrow>
   </mrow>
</math> <br/> <br/>

<math>
   <mi>E</mi>
   <mo>=</mo>
   <mfenced>
   <mtable>
      <mtr>
         <mtd><mn>1</mn></mtd>
         <mtd><mn>0</mn></mtd>
         <mtd><mn>0</mn></mtd>
      </mtr>
      <mtr>
         <mtd><mn>0</mn></mtd>
         <mtd><mn>1</mn></mtd>
         <mtd><mn>0</mn></mtd>
      </mtr>
      <mtr>
         <mtd><mn>0</mn></mtd>
         <mtd><mn>0</mn></mtd>
         <mtd><mn>1</mn></mtd>
      </mtr>
   </mtable>
</math> <br/> <br/>

<math>
   <mi>c</mi>
   <mo>=</mo>
   <msqrt>
      <msup><mi>a</mi><mn>2</mn></msup>
      <mo>+</mo>
      <msup><mi>b</mi><mn>2</mn></msup>
   </msqrt>
</math>

</body></html>