AB = diameter of the circle = 8 cm. Also, since the angle inscribed in a semicircle is a right angle, ∴ Triangle ABC is a right-angled triangle. ∴ By the Pythagorean theorem: AC² + BC² = AB² ⇒ AC² + (2√7)² = 8² ⇒ AC² + 28 = 64 ⇒ AC² = 64 - 28 = 36 ⇒ AC = √36 = 6 ∴ The length of AC is 6 cm.