Given : OB is the radius of circle = 5 cm and OC = 4 cm To find : AB = ? Solution : The line from the centre of the circle to the chord bisects it at right angle. ⇒ AC = BC =
1
2
AB In ∆OBC, ⇒ (BC)2=(OB)2−(OC)2 ⇒ (BC)2=(5)2−(4)2 ⇒ (BC)2=25−16=9 ⇒ BC=√9=3cm ∴ AB = 2 × BC = 2 × 3 = 6 cm