Question

the length of a tangent from a point a at a distance 5 cm from the circle is 4 cm find the radius of the circle

Answer 1

given ;  a circle with centre o and radius r.

AB is a tangent. Therefore, OB ⊥ AB

In right triangle OBA, using P.G.T.

(OA)²= (OB)² + (AB)²

(5)² = (OB)² + (4)²

25 = (OB)² + 16

25 - 16 = (OB)²

9 = (OB)²

√9 = OB

OB = 3 cm