Question

Записать в виде произведения
cos12+cos42+cos72+cos102

Answer 1

Ответ:     2cos57°cos15° .

Объяснение:

cos12°+cos42°+cos72°+cos102° = (cos102°+ cos12° ) + (cos72°+cos42° ) =

= 2cos57°cos90° + 2cos57°cos15° =2cos57° * 0 + 2cos57°cos15° =

= 0 + 2cos57°cos15° = 2cos57°cos15° .