The expression is .
Consider .
Apply reciprocal identities :
.
Apply quotient identity : .
Apply pythagorean identity : .
..
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.![\"\"](\"http://www.mathskey.com/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=be8bb17d0bfcdcaa56fea5c3fd250156.png\")
.![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=318ce3f6fc96a20f51a23cb53fad90ee.png\")
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.![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=ac4c009551848514c351ecd3e2a20c76.png\")
.![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=b03610c8fa3adf98e5724464a2e99123.png\")
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.![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=6dbda94ef14ad0f45b83c0a0d466688b.png\")
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.![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=2f863e7e3078539a716801ff4cb1a173.png\")
..![\"\"](\"http://www.mathskey.com/userfiles/image/steps_images/solution.JPG\")
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.