2

Part of 1982 Austrian-Polish Competition

Problems(1)

at each point one can draw two rays tangent to F of angle of 60^o, locus

Source: Austrian Polish 1982 APMC

F

be a closed convex region inside a circle

C

O

1

. Furthermore, assume that from each point of

C

one can draw two rays tangent to

F

which form an angle of

60^o

F

is the disc centered at

O

1/2

LocusTangentscircleconvexgeometry