i need to answer a question related to trigonometry urgently

Dec 2008
7
0
i have to evaluate without using a calculator
cos 165
can someone help me out
 
May 2008
400
82
Ottawa, Canada
i have to evaluate without using a calculator
cos 165
can someone help me out
cos165=cos(120+45)
=cos120cos45-sin120sin45
=(-1/2)(sqrt2/2)-(sqrt3/2)(sqrt2/2)
=-sqrt2-sqrt4/6

is that what you need?
 
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