Given: Diameter AB and a chord AC have a common end point A. AB = 20 cm and AC = 12 cm. To determine: OD
Determination: ∵ OD ⊥ AC
| ∵ The perpendicular drawn from the centre of a circle to a chord bisects the chord.
In right triangle ODA,
OA2 = OD2 + AD2
| By Pythagoras Theorem
⇒ (10)2 = OD2 + (6)2
⇒ OD = 8 cm
Hence, AC is 8 cm far from the centre of the circle.