Question 766937: use an appropriate identity to find the exact value of the expression
cos (5pi/12) Found 2 solutions by stanbon, josgarithmetic:Answer by stanbon(75887) (Show Source):
You can put this solution on YOUR website! use an appropriate identity to find the exact value of the expression
cos (5pi/12)
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5/12 = 1/6 + 1/4 = 10/24 = 5/12
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cos(5pi/12) = cos[pi/6+pi/4] = cos(pi/6)cos(pi/4) - sin(pi/6)sin(pi/4)
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= (sqrt(3)/2))(sqrt(2)/2) - (1/2)(sqrt(2)/2)
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= (sqrt(6))/4 - (sqrt(2))/4
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= [sqrt(6)-sqrt(2)]/4
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Cheers,
Stan H.
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