Mathematics

Problem

Let A, B, C are three points in x-y plane such that

OA = 2

OB = 2

OC = 3

and

AB^2 + BC^2 + CA^2 = 51

then the distance between O and D is (where D is mid point of AB and O is origin) (a)

\frac{1}{2}

(b) 2 (c)

\frac{3}{2}

(d)

\frac{5}{2}