Pythagorean theorem shows that AC= root sign (10* 10-8*8)=6(cm) and OC=3cm.

Pythagorean theorem shows that OB= root number (3*3+8*8)= root number 73(cm).

It is proved that the triangle ABE congruent triangles CDF is parallel and equal to DF, and the quadrilateral BEDEF is a parallelogram.