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calculus

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Cos(pi/12) solve using half angle formula

  • calculus -

    cos 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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