Respuesta :

Use Pythagorean's Theorem here.  If BC is a tangent, the point where it meets the circle, the point of tangency, is a right angle.  [tex]10 ^{2} -6 ^{2} = x^{2} [/tex] 100-36=64 and the square root of 64 is 8.  So x = 8, choice a from above.