\
The expression is
.
\
Apply product-to-sum identities :
.
\
\
\
The exact value of
is
.
![\"\"](\"http://www.mathskey.com/userfiles/image/steps_images/step1.JPG\")
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=e748710417a9807a0400283d4c167d0e.png\")
.![\"\"](\"http://www.mathskey.com/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=0852372c77dff45c9cd823734e1156a1.png\")
.![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=3024e5c05a573bf658ef3c98096b0b80.png\")
![\"\"](\"http://www.mathskey.com/userfiles/image/steps_images/solution.JPG\")
![\"\"](\"http://www.mathskey.com/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=e748710417a9807a0400283d4c167d0e.png\")
is ![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=56c26fec1c923cfe00a19d60f7ba79b6.png\")
.