Test using functions as arguments to other operators
<math xmlns="http://www.w3.org/1998/Math/MathML"> <apply> <csymbol cd="arith1">plus</csymbol> <apply> <csymbol cd="arith1">power</csymbol> <csymbol cd="transc1">sin</csymbol> <cn>2</cn> </apply> <apply> <csymbol cd="arith1">power</csymbol> <csymbol cd="transc1">cos</csymbol> <cn>2</cn> </apply> </apply> </math>