cos π/2=0
Объяснение:
cos(a+b)=cos a cos b - sin a sin b
cos (3π/8 +π/8) = cos 4π/8 = cos π/2=0
cosacosb–sinasinb = cos(a+b)
Отсюда:
cos(3п/8)cos(п/8)–sin(3п/8)sin(п/8) = cos(3п/8+п/8) = cos(4п/8) = cos(п/2) = 0
