Question

Срочно!
cos27°cos63° - sin27°sin63°

Answer 1

cos27°cos63° - sin27°sin63° = cos27°sin27° - sin27°cos27° = 0

Answer 2

Это косинус суммы:  

cosα·cosβ - sinα·sinβ = cos(α+β)

cos27°cos63° - sin27°sin63° = cos(27°+63°) = cos90° = 0