cos130 градусов*cos40градусов+sin40градусов*sin130градусов

Question

cos130 градусов*cos40градусов+sin40градусов*sin130градусов

Answer 1

по формуле

cos(α - β) = cosα cosβ + sinα sinβ

 

cos(130-40)=cos90=0

Answer 2

cos130°*cos40°+sin40°*sin130°=cos(130°-40°)=cos90°=0.