The identity is .
(Apply difference of angles formula: )
(Substitute )
(Multiply)
(Simplify)
is an identity.
![\"\"](\"http://www.mathskey.com/userfiles/image/steps_images/step1.JPG\")
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=c3e8a04aa380667c8d037642f38e79aa.png\")
.![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=6eccee0f5c434f2f205ad8bf50a7e2a0.png\")
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=14f23f8cd4ec05ff916ee79cf444a66b.png\")
)![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=6bbe4f035d8dce5405297f29abc7fb6e.png\")
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=49be800d9e8acd08dbc7d582371db2a0.png\")
(Substitute ![\"\"](\"http://www.mathskey.com/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=06e5bfa7e9863e46256e9c19747de7d2.png\")
)![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=8028aa7ff98a177ef0e3d501981f5c61.png\")
(Multiply)![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=40c2d089c09c566ca161929b33878d0d.png\")
(Simplify)![\"\"](\"/userfiles/image/steps_images/solution.JPG\")
![\"\"](\"http://www.mathskey.com/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=c3e8a04aa380667c8d037642f38e79aa.png\")
is an identity.