MathML generated by MathToWeb
A MathML example displaying boldface letters, signifying vectors in this case, by way of the AMS Latex command   \mathbf{A}.

$\mathbf{A}={\mathbf{r}}_2-{\mathbf{r}}_1$ $\mathbf{A} = \mathbf{r}_2 - \mathbf{r}_1$

<math xmlns="http://www.w3.org/1998/Math/MathML">
<mrow>
	<mi mathvariant="bold">A</mi>
	<mo>=</mo>
	<msub>
		<mi mathvariant="bold">r</mi>
		<mn>2</mn>
	</msub>
	<mo>-</mo>
	<msub>
		<mi mathvariant="bold">r</mi>
		<mn>1</mn>
	</msub>
</mrow>
</math>