@Joe Riel 

Thak yous so much it worked! =)

Thanks for your speedy reply, however this method doesn't produce the correct answer. Here are the answers it should produce

phi1:=6.61943275102

phi2:= 13.2388656192415937

phi3:= 19.8582984789843700

etc

The method I have used does work but it isn't very efficient.

Regards,

Fran

@Adri van der Meer