cos72+cos12/sin12-sin72

cos72 + cos12 = 2 cos (72 + 12)/2 * cos (72 - 12)/2 =  = 2 cos 42 * cos 30sin12 - sin72 = 2 sin (12 - 72)/2 * cos (12 + 72)/2 = = - 2 sin30 * cos 42(2 cos 42 * cos 30) / (- 2 sin30 * cos 42 ) = = (cos 30) / ( -  sin30 ) = = - ctg30 = - √3Ответ- √3