O is the origin. ABCDEF is a regular hexagon, and the midpoint of AD is O, and OC=c. Find the length of OA and OC in simplest form.
a) OA = c/√3, OC = c
b) OA = c√3/2, OC = c
c) OA = c/2, OC = c
d) OA = c, OC = c√3