Firstly, create a right angled triangle. The first side should be 3cm using the y-coordinates, from (9-6). The next side should be 6cm, calculated using the x-coordinates, from (11-5).Pythagoras' theorem uses the equation a² + b² = c². Therefore, if you sub in the values you are left with 6² + 3² = c².This forms 36 + 9 = c². So 45 = c². To find out what c is, you square root 45 = √45Therefore c = 6.7cm (to 1 d.p.)