SOLUTION: find the exact value of cos 105degrees. without the table or calculator.

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Question 207434: find the exact value of cos 105degrees. without the table or calculator.
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
find the exact value of cos 105degrees. without the table or calculator.
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cos(105) = cos(45+60) = cos(45)cos(60)-sin(45)sin(60)=
= (sqrt(2)/2)(1/2)-(sqrt(2)/2)(sqrt(3)/2)
= (sqrt(2)/4 - (sqrt(6)/4)
= [sqrt(2)-sqrt(6)]/4
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Cheers,
Stan H.