What is the measure of the secant DC?
Look at the graph
http://assets.openstudy.com/updates/attachments/511d393ee4b06821731b8043-dmainasdoia-1360869738952-asdasd.png

Question

What is the measure of the secant DC?
Look at the  graph
http://assets.openstudy.com/updates/attachments/511d393ee4b06821731b8043-dmainasdoia-1360869738952-asdasd.png

directrix · Answer

Theorem:

If two secant segments share the same endpoint outside a circle, 
then the product of the length of one secant segment and the length of its external segment equals the product of the length of the other secant segment and the length of its external segment.

directrix · Answer

That translates to, in this problem, to:

BC * AC = CD * EC

4( 6.5 + 4) = CD * 14

Solve the equation for CD.