In the figure below, a tangent and a secant are drawn to a circle from exterior point E. Suppose that EC= 10.8 and EG= 18. Find CD.

Answer: 19.2
Step-by-step explanation:
Using power of a point with respect to a circle:
EG²=EC*ED ==> ED=18²/10.8=30
CD=ED-EC=30-10.8=19.2