Question

Cos(a-b)-2sinasinb/2sinacosb-sin(a-b)
Помогите пожалуйста)

Answer 1

1)cos(a+b)+2sinasinb/2sinacosb-sin(a+b)=
(cosacosb-sinasinb+2sinasinb)/(2sinacosb-sinacosb-cosasinb)=
=(cosacosb+sinasinb)/(sinacosb-cosasinb)=cos(a-b)/sin(a-b)=ctg(a-b)