Question:
A tangent PQ at a point P of a circle of radius 5 cm meets a line through the centre O at a point Q so that OQ = 12 cm. Length PQ is.
(1) 12 cm
(2) 13 cm
(3) 8.5 cmÂ
(4) $\sqrt{119} \mathrm{~cm}$
Solution:
O is the centre of the circle. The radius of the circle is 5 cm.
PQ is tangent to the circle at P. Then
$\mathrm{OP}=5 \mathrm{~cm}$ and $\angle \mathrm{OPQ}=90^{\circ}$
We are given that $\mathrm{OQ}=12 \mathrm{~cm}$.
By Pythagoras Theorem, we have
$\mathrm{PQ}^{2}=\mathrm{OQ}^{2}-\mathrm{OP}^{2}$
$=(12)^{2}-(5)^{2}=144-25=119$
$\Rightarrow \mathrm{PQ}=\sqrt{\mathbf{1 1 9}} \mathrm{cm}$
Hence, the correction option is (D).
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