Golden pentagon construction

I’m a little obsessed with proportions right now, as can probably be seen by my recent posts. I’m trying to tie down everything I know about type and layout by going back to the beginning and getting my head around what is basically the fun, or at least less dull, side of maths (geometry). I’m beginning to regret having done French at a-level…. Should have done maths! I made my own drawing of the pentagon/decagon construction but thought it could be done in another way and, surely, with more ease. I was right! So, in a later post, my own method will be shown.