sin(4a)*ctg(2a) - cos(4a)
sin4a*ctg2a - cos4a = 2sin2a*cos2a*cos2a/sin2a - cos4a = 2cos²2a - cos4a = 1 + cos4a - cos4a = 1
sin(4a)*ctg(2a) - cos(4a)
sin4a*ctg2a - cos4a = 2sin2a*cos2a*cos2a/sin2a - cos4a = 2cos²2a - cos4a = 1 + cos4a - cos4a = 1