Exercise 6 - updated version includes calculation of minimum & maximum points
Exercise 7 - updated to correct typo: equilateral replaced by isosceles
Exercise 9 - updated to make the proof easier to follow 19/01/2015
Exercise 10 - updated to change equilateral to isosceles & clarify 18/01/2015
Exercise 12 - updated 25/7/2014 to correct typo in figure 2 (see blog for details)
Exercise 13 - updated 12/10/2014 (see blog for details)