Cos (d+B) -cosd ×cosB =??

Question

Cos (d+B) -cosd ×cosB =??

Answer 1

Воспользуемся формулой
cos(α+β) = cos(α)·cos(β) - sin(α)·sin(β)

Упростим
cos(d + b) = cosd·cosb - sina·sinb
cosd·cosb - sina·sinb -  cosd·cosb  =  - sina·sinb