000RM.dvi

11.4 Construction of regular pentagon 327

11.4 Construction of regular pentagon

LetOAandOYbe two perpendicular radii of a circle, centerO.

1.Mark the midpointMofOYand bisect angleOMAto intersect

OAatP.

2.Construct the perpendicular toOAatPto intersect the circle atB

andE.

A

Y

M

P

B

E

O

C

D

ThenA,B,Eare three adjacent vertices of a regular pentagon in-
scribed in the circle. The remaining two vertices can be easily con-
structed.