Ответ:

Пошаговое объяснение:

1)  cos2+sin84=cos2+sin(90-6)=cos2+cos6=

=2cos((6+2)/2)cos((6-2)/2)=2cos4cos2

2) √2/2-sin5=cos(360k+-45)-sin(90-85)=cos(360k+-45)-cos85=

=-2sin((360k+85+-45)/2)sin((360k-85+-45)/2) =

2.1  =-2sin((360k+85+45)/2)sin((360k-85+45)/2)=

      =-2sin(180k+65)sin(180k-20)

2.2 =-2sin((360k+85-45)/2)sin((360k-85-45)/2)=

      =-2sin(180k+20)sin(180k-65)