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In the figure triangle $ABC$ is right-angled at $B$. Given that $AB = 9\ cm, AC = 15\ cm$ and $D, E$ are the mid points of the sides $AB$ and $AC$ respectively, calculate the length of $BC$.
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Academic Mathematics NCERT Class 9

Given:

In the figure triangle $ABC$ is right-angled at $B$, $AB = 9\ cm, AC = 15\ cm$ and $D, E$ are the mid points of the sides $AB$ and $AC$ respectively.

To do:

We have to calculate the length of $BC$.

Solution:

In $\mathrm{ABC}, \angle \mathrm{B}=90^{\circ}$

$A C^{2}=A B^{2}+B C^{2}$ (Pythagonas Theorem)

$\Rightarrow B C^{2}=A C^{2}-A B^{2}$

$=(15)^{2}-(9)^{2}$

$=225-81$

$=144$

$=(12)^{2}$

$B C=12 \mathrm{~cm}$.

Updated on: 10-Oct-2022

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