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From a point $Q$, the length of the tangent to a circle is $24$ cm and the distance of $Q$ from the centre is $25$ cm. The radius of the circle is
(a) 7 cm
(b) 12 cm
(c) 15 cm
(d) 24.5 cm
Given:
From a point $Q$, the length of the tangent to a circle is $24$ cm and the distance of $Q$ from the centre is $25$ cm.
To do:
We have to find the radius of the circle.
Solution:
We know that,
The tangent to a circle is perpendicular to the radius through the point of contact.
$\angle OPQ = 90^o$
Therefore, by Pythagoras theorem,
$PQ^2+OP^2 = OQ^2$
$OP^2=OQ^2-PQ^2$
$OP^2 = (25)^2 - (24)^2$
$= 625 - 576$
$= 49$
$OP = \sqrt{49}\ cm$
$OP=7\ cm$
Therefore, the radius of the circle is $7\ cm$.
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