hello everyone i am looking at following problem from this link
http://web.gnowledge.org/wiki/index.php/Solution_to_length_of_the_belt
it is possible to say that everything is explained detailed but i did not understand some of them 1.what about number 7?how is here written 7 without explanation what does it mean?then why is here mentioned semicircles i am confused about it it is drawn simple two circles please help me to understand everything given in above mentioned task