def removeDoubles(begin):  
	# "remove doubles means keeping only one of Eq and -Eq on the list, to get 270."
	# toTreat keeps a list of eqns that are yet to be treated. In the beginning, it is just a copy of the singleton list of equations.
	equationsNoDoubles = set([])
	toTreat = begin.copy()
	#Treated keeps a list of the equations that have been treated.
	treated = set([]) 

	while len(toTreat) > 0:
		# Pick the first equation to be treated
		eq = SR(expand(toTreat.pop()))
	# Add to equations the (previously unseen) equations unless it is obtained by multiplying by -1
		newEq = SR(expand(-1*eq))
		if newEq not in equationsNoDoubles and eq not in equationsNoDoubles:
			equationsNoDoubles.add(eq)
		        treated.add(eq)

		print "Found: " + str(len(equationsNoDoubles))
		print "To treat: " + str(len(toTreat))
		print "Treated: " + str(len(treated))
		print " "
	return(equationsNoDoubles)