Respuesta :

Solution:
(tanx + tany)/(1-tanxtany) is equal to the formula of  tan(x+y) 
sinxcosy + cosxsiny =  is equal to the formula of sin(x+y)formula 
cosxcosy - sinxsiny) = is equal to the formula of cos(x+y) 

So this means that
 tan(x+y) = sin(x+y)/cos(x+y)