In fig. a circle is inscribed in a triangle ABC, touches its sides \ AB, BC and AC at points D, E and F respectively.If $AB=12\ cm,\ BC=8\ cm$,Then find the length of AD, BE and CF.


Given: O is the center of a circle such that diameter $AB= 13\ cm$ and $AC =12\ cm$. $BC$ is joined. 

To do: To find the area of the shaded region.

Solution:

Diameter, $AB = 13\ cm$

$\therefore$  Radius of the circle, $r =\frac{13}{2}$

$=\ 6.5\ cm$

$\angle ACB$ is the angle in the semi-circle.

$\therefore \ \angle ACB=90^{o}$

Now, in $\vartriangle ACB$, using Pythagoras theorem, we have

$AB^{2} =AC^{2}+BC^{2}$

$( 13)^{2}=( 12)^{2}+( BC)^{2}$

$( BC)^{2}=( 13)^{2} –( 12)^{2} =169–144=25$

$BC=\sqrt{25}$

$=5\ cm$

Now, Area of shaded region $=$ Area of semi-circle$-$Area of the $vartiangle ABC$

$=66.33 –30$

$=36.33\ cm^{2}$

Thus, The area of the shaded region is $36.33\ cm^{2}$.

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Updated on: 10-Oct-2022

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