what is the formula to find chord in a circle
Since this is not my area of expertise, I searched Google under the key words "formula circle chord" to get these possible sources:
http://mathcentral.uregina.ca/QQ/database/QQ.09.05/bes1.html
http://library.thinkquest.org/20991/geo/circles.html
http://www.mathwarehouse.com/geometry/circle/chord-of-circle.php
http://en.wikipedia.org/wiki/Circle
In the future, you can find the information you desire more quickly, if you use appropriate key words to do your own search.
I hope this helps. Thanks for asking.