MCQ
In the given figure,$ \triangle\text{ABC}$ is right$-$angled at $B,$ such that $BC = 6\ cm$ and $AB = 8\ cm$. A circle with centre $O$ has been inscribed in the triangle. $\text{OP} \perp \text{AB}, \text{OQ} \perp \text{BC} $ and $\text{OR} \perp \text{AC}.$ If $\text{OP = OQ = OR} = x \ cm,$ then $x =?$
  • $2\ cm$
  • B
    $2.5\ cm$
  • C
    $3\ cm$
  • D
    $3.5\ cm$

Answer

Correct option: A.
$2\ cm$
In right $\triangle\text{ABC},$
$\text{AC}^2=\text{AB}^2+\text{BC}^2 ....($By Pythagoras theorem$)$
$\Rightarrow\text{AC}^2=8^2+6^2$
$\Rightarrow\text{AC}^2=64+36$
$\Rightarrow\text{AC}=100$
$\Rightarrow\text{AC}=10\text{cm}$
We know that tangent from an external poit to the circle are equal.
$\Rightarrow\text{CR}=\text{CQ}=\text{BC}-\text{BQ}=(6-\text{x})\text{cm}$
$\Rightarrow\text{AR}=\text{AP}=\text{AB}-\text{BP}=(8-\text{x})\text{cm}$
$\text{AC}=(\text{AR}+\text{CR})=(8-\text{x})+(6-\text{x})=(14-2\text{x})\text{cm}$
$\Rightarrow14-2\text{x}=10$
$\Rightarrow2\text{x}=4$
$\Rightarrow\text{x}=2$

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