O is the centre of a circle of radius 9 cm. M is a point outside the circle and MN is a tangent to the circle. What is the length (in cm) of OM if the length MN is 12 cm?
Answer & explanation
Correct answer: option 3
We know that,
Radius = 9 cm.
MN is a tangent to the circle and also tangent is perpendicular to radius.
MN = 12 cm
Tangent is perpendicular to radius = ∠OPR = 90°
We also know that,
= OM2 = OP2 + PM2
= OM = √(92 + 122)
= √225 = 15 cm