1 - cos4x / sin4x * ctg2x = 1 - cos(4*pi/12) / sin(4*pi/12) * cos(2*pi/12) / sin(2*pi/12) = 1 - cos(pi/3) / sin(pi/3) * cos(pi/6) / sin(pi/6) = 1 - 1/2 / (√3/2) * (√3/2) / (1/2) = 1 - 1/2 / (1/2) = 1 - 1 = 0.

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