Let be A the point where the tan & the secante intersect out of the circle
and let AT be tan in T & B, C the intersection with the circle
When a tan & a secante are drawn from a same point outside a circle, we hava the following formula:
AT² = AB x AC
6² = 3 x AC===> 36=3xAC & AC =12
WE know AC = AB + c . Calculate c=AC-AB=> c =9 (answer C)
