Tick the correct answer and justify : In $∆ABC, AB = 6\sqrt3\ cm, AC = 12\ cm$ and $BC = 6\ cm$. The angle B is:
(a) $120^o$
(b) $60^o$
(c) $90^o$
(d) $45^o$

AcademicMathematicsNCERTClass 10

Given:

In $∆ABC, AB = 6\sqrt3\ cm, AC = 12\ cm$ and $BC = 6\ cm$.

To do: 

We have to find angle B.

Solution:

$AC^{2}=(12)^2$

$=144$

$A B^{2}+B C^{2}=(6 \sqrt{3})^{2}+(6)^{2}$

$=108+36$

$=144$

$AC^2=A B^{2}+B C^{2}$

This implies,

Triangle ABC is a right angle triangle, right angled at $B$. 

$\angle B =90^{\circ}$

raja
Updated on 10-Oct-2022 13:21:38

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