Question

косинус(α-β)+ синус(-α)синусβ- косинусα*косинусβ

Answer 1

$cos( alpha - beta )+sin(- alpha )sin beta -cos alpha cos beta = \ =cos alpha cos beta +sin alpha sin beta -sin alpha sin beta -cos alpha cos beta = \ =0$

Answer 2

$cos(a-b)+sin(-a)sinb-cosacosb=cosacosb+sinasinb- \ -sinasinb-cosacosb=0$