Интересный учебник по математике

https://books.google.com.ua/books?id=A8f9AgAAQBAJ&pg=PA382&lpg=PA382&dq=как+отдыхают+математики&source=bl&ots=Zok00fUFG5&sig=Q4or5HEXWrtGOsIKwtK4otmlvlI&hl=uk&sa=X&sqi=2&ved=0ahUKEwjoy-XK95fNAhUG3iwKHVZ4BHAQ6AEIRjAH#v=onepage&q=%D0%BA%D0%B0%D0%BA%20%D0%BE%D1%82%D0%B4%D1%8B%D1%85%D0%B0%D1%8E%D1%82%20%D0%BC%D0%B0%D1%82%D0%B5%D0%BC%D0%B0%D1%82%D0%B8%D0%BA%D0%B8&f=false