Hi all. I'm looking at some old Maths exam papers at the moment and there is one particular type of question that has me stumped. They look just like basic geometry questions of the type I can normally do, but I think I'm missing something in these particular problems as I'm getting stuck. I've uploaded an example of the type under consideration and would really appreciate a hand getting started with it. Ideally if someone could just explain how to get the answer in part (i) I'd like to see if I can take it from there. Thanks.