https://math.ucr.edu/home/baez/klein.html
замощения сферы одинаковым правильными сферическими многоугольниками соответствуют правильным многогранникам
а что хорошего можно сделать из замощений плоскости Лобачевского?
если правильным образом их покрасить, а потом отождествить части одного цвета, можно получить интересные римановы поверхности
по ссылке объясняется, например, как таким образом получить квартику Клейна
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Yes! Voice calls are currently available to users around the world.
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