Вопрос для Илюхи:
cos70 +sin140-cos10=
Илюха-Отвечает:
cos70-cos10=-2sin(70+10)/2sin(70-10)/2=-2sin40sin30=-2*(1/2)sin40=-sin40 sin140-sin40=2sin(140-40)/2cos(140+40)/2=2sin50cos90=0
cos70 +sin140-cos10=
cos70-cos10=-2sin(70+10)/2sin(70-10)/2=-2sin40sin30=-2*(1/2)sin40=-sin40 sin140-sin40=2sin(140-40)/2cos(140+40)/2=2sin50cos90=0