A circle is a curve sketched out by a point moving in a plane. The radius of the given circle is 8.4 units. The correct option is D.
What is a circle?
A circle is a curve sketched out by a point moving in a plane so that its distance from a given point is constant; alternatively, it is the shape formed by all points in a plane that are at a set distance from a given point, the centre.
In a circle, a tangent is always perpendicular to the radius of the circle. Therefore, in the given figure the triangle formed will be a right angled triangle.
Now, in a right angle triangle, using the Pythagoras theorem the relation between the different sides of the triangle can be written as,
AO² = AB² + OB²
(9.8)² = 5² + r²
96.04 = 25 + r²
r² = 96.04 - 25
r² = 71.04
r = √(71.04)
r = 8.4
Hence, the radius of the given circle is 8.4 units.
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