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cos74+cos62+cos50

cos74+cos62+cos50 = (cos74+cos50) + cos62=2cos ((74+50) / 2) * cos ((74-50) / 2) + cos62=2cos 62*cos12+cos62=cos62 (2cos12+1) = 2*cos62 (cos12+1/2) = 2*cos62 (cos12+cos60) = 2*cos62*2*cos ((60+12) / 2) * cos ((60-12) / 2) = 4*cos62*cos36*cos24