Question

(sin(a+b)-2cos a sin b)/ 2sina sinb+cos(a+b))

Answer 1

$\frac{sin(a+b)-2cos(a)sin(b)}{ 2sin(a)sin(b)+cos(a+b))}=\frac{sin(a)cos(b)+sin(b)cos(a)-2cos(a)sin(b)}{2sin(a)sin(b)+cos(a)cos(b)-sin(a)sin(b)}\\ \frac{sin(a)cos(b)-cos(a)sin(b)}{cos(a)cos(b)+sin(a)sin(b)}=\frac {sin(a-b)}{cos(a-b)}=tg(a-b)$