radius circumscribed circle isosceles trapezoid

a12 green    - equal sides of a trapezoid

b brown ,  c orange  - bases

d blue1  - diagonal    

s (abc)2 orange

s (abc)2 brawn

O black  - circumcenter    

Calculate the radius of the circumcircle of an isosceles trapezoid if given sides and diagonal ( R  ) :

radius circumscribed circle isosceles trapezoid F5

radius circumscribed circle isosceles trapezoid F6