Question

Show that tanx= (sinx/ cosx)
can be written as:
tan(x-y) = (tanx - tany) / (1+ tanxtany)

Answer 1

write tan (x-y)
= sin(x-y)/cos(x-y)
= [sinxcosy - cosxsiny[/[cosxcosy + sinxsiny]

Now divide everybody by cosxcosy and it will all fall into place.