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March 29, 2015

March 29, 2015

Posted by **Abbey** on Sunday, February 5, 2012 at 11:05pm.

- calculus -
**Reiny**, Monday, February 6, 2012 at 12:52amcos 2A = 2cos^2 A - 1

cos (π/6) = 2cos^2 (π/12) - 1

√3/2 + 1 = 2cos^2 (π/12)

cos π/12 = ±√(√3/4 + 1/2)

but /12 is in quadrant I

so cos (π/12) = √(√3/4 + 1/2)

or (1/2)√(√3 + 2)

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