MathDB

Streets of Moscow are some circles (rings) with common center

O

and some straight lines from center

O

to external ring. Point

A,B

- two crossroads on external ring. Three friends want to move from

A

B

. Dima goes by external ring, Kostya goes from

A

O

then to

B

. Sergey says, that there is another way, that is shortest. Prove, that he is wrong.

Problem Statement