SOLUTION: sec(-7pi/12) using difference and sum identities

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Question 1018570: sec(-7pi/12)
using difference and sum identities
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
sec(-7pi/12)
using difference and sum identities
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sec(-7pi/12) = 1/[cos(-7pi/12)]
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= 1/[cos(-3pi/12)-4pi/12]
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= 1/[cos(-pi/4 +(-pi/3))]
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= 1/[cos(-pi/4)*cos(-pi/3) - sin(-pi/4)*sin(-pi/3)]
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= 1/[(sqrt(2)/2)(1/2) - (-sqrt(2)/2)(-sqrt(3)/2))
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= 1/[(sqrt(2)/4) - (sqrt(6))/4]
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= 4/[sqrt(2)-sqrt(6)]
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Cheers,
Stan H.
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