2017.C1

Part of Durer Math Competition CD 1st Round - geometry

Problems(1)

angle between 2 digaonals of regular 10-gon 2016-17 Dürer Round1 C1

Source:

The vertices of Durer's favorite regular decagon in clockwise order:

D_1, D_2, D_3, . . . , D_{10}

. What is the angle between the diagonals

D_1D_3

D_2D_5

DurergeometryanglesDecagon