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[ª] , [©] , [^]
, [¨]Perimeter of triangle which inscribes in a circle / Decoding the meaning of additional line**(GC World : Various Problems ,MaxEMin)

A, B, and C are on a circle O.

When will the perimeter of ƒ¢ABC be maximized/minimized?

What is the role of this line?

GC/Win