\
The expression is
.
\
Trigonometric even-odd properties :
.
\
\
\
.
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=de3f87bf41eec11b55c6ee56ff9ea687.png\")
..![\"\"](\"http://www.mathskey.com/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=3ccf255cc3682ce6274c00eb830850e2.png\")
.![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=60da4232e57ebc478df86175e64e1fe1.png\")
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=fdb5585b50ff74594b54076a0927d630.png\")
.