Fairly comprehensive test of many mfrac properties
<math xmlns="http://www.w3.org/1998/Math/MathML"> <mtext>Inline double up arrows, auto, thick line </mtext> <mstyle displaystyle="false" scriptlevel="0"> <mrow> <mo form="prefix" fence="true" stretchy="true" lspace="0em" rspace="0em">⇑</mo> <mfrac linethickness="1pt"> <mrow> <mi mathcolor="gray">sin</mi> <mo rspace="verythinmathspace">⁡</mo> <mi>θ</mi> </mrow> <mi>M</mi> </mfrac> <mo form="postfix" fence="true" stretchy="true" lspace="0em" rspace="0em">⇑</mo> </mrow> </mstyle> <mtext> the end.</mtext> </math>