Ответ:

Объяснение:

[tex]\frac{cos(a)cos(b) - sin(a)sin(b) + cos(a)cos(b) + sin(a)sin(b)}{sin(a)cos(b) + sin(b)cos(a) - sin(a)cos(b) + sin(b)cos(a)} = \frac{2cos(a)cos(b)}{2sin(b)cos(a)} = \frac{cos(b)}{sin(b)} = ctg(b)[/tex]