The trigonometric expression is .
.
Apply complementary angle theorem: and .
Apply Pythagorean identity: .
![\"\"](\"/userfiles/image/steps_images/step1.JPG\")
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=aec27b37a6ecf79f46e284291eca6228.png\")
. ![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=36aca85a1498e1258c18db90ebc920cf.png\")
.![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=7b4f701f7f33356e6225ba9a76d32c1c.png\")
and ![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=103da573978985a7dda6a31203d76a0b.png\")
. ![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=4f5a41959c761ffe88812622d399e96f.png\")
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=b4226d02635dfd4d66b7c9466701c9c7.png\")
![\"italic](\"http://www.wiris.com/demo-aspx/pluginwiris3/fckeditor_wiris/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.aspx?formula=71551fa865beeb60e69b8bcd87a295be.png\")
.![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=a83e6cd324af1446966a4fa704ade5da.png\")
. ![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=a5a2af483944a1e3a52b9abf0eae0973.png\")
. ![\"\"](\"/userfiles/image/steps_images/solution.JPG\")
![\"\"](\"http://www.mathskey.com/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=a5a2af483944a1e3a52b9abf0eae0973.png\")
.