A tangent to a circle has length 8 cm, and the shortest distance from the external point to the circle is 4 cm. What is the radius of the circle?
Show answer & explanation
Correct answer: A
Explanation
Radius of the circle = r
Distance from the external point to the center = r + 4
Length of the tangent = 8 cm
(Distance from the external point to the center)² = (Tangent)² + (Radius)²
(r + 4)² = 8² + r²
r² + 8r + 16 = 64 + r²
8r = 48
r = 6 cm