Let C' be the midpoint of the side AB. Prove that (CH)/(OC')=2.

For the following problems consider a triangle ABC. a,b,c denote the lengths of the sides opposite to A,B,C respectively. S denotes the area of the triangle. p= (a+b+c)/2 is the semi-perimeter of the triangle. R is the radius of the circumscribed circle and r is the radius of the inscribed circle. O,G,H,I are the circumcenter, centroid, orthocenter and incenter respectively.

prove:

Let C' be the midpoint of the side AB. Prove that (CH)/(OC')=2.