inverse matrix
<math xmlns="http://www.w3.org/1998/Math/MathML"> <apply> <apply> <csymbol cd="fns1">inverse</csymbol> <semantics> <ci>a</ci> <annotation-xml cd="mathmltypes" name="type" encoding="MathML-Content"> <ci>matrix</ci> </annotation-xml> </semantics> </apply> <ci>A</ci> </apply> </math>