по формуле
cos(α - β) = cosα cosβ + sinα sinβ
cos(130-40)=cos90=0
cos130°*cos40°+sin40°*sin130°=cos(130°-40°)=cos90°=0.
по формуле
cos(α - β) = cosα cosβ + sinα sinβ
cos(130-40)=cos90=0
cos130°*cos40°+sin40°*sin130°=cos(130°-40°)=cos90°=0.