Hello everybody, this is my first post!

How do I find the radius of a circle that is in side a diamond/ rombus? The quadrilateral has 2 diagonals of 10 and 20cm. I have got as far as finding that if you cross the diagonals you get 4 triangles and i have found that the sides of the diamond are 22.36cm. I cant get any further! Help pleaase.

Thank you.