The given trigonometric expression is .
(Using the formula: )
Apply pythagorean identity: .
The solution is .
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(Using the formula: ![\"\"](\"http://www.mathskey.com/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=d241484fd8966126f5767ca711f1d35d.png\")
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.