Question
In a $\triangle\text{ABC},$ if $\angle\text{A}=120^\circ$ and $\text{AB}=\text{AC}.$ Find $\angle\text{A}$ and $\angle\text{C}.$
✓
Answer
Consider a $\triangle\text{ABC}.$ 
Given Mat $\angle\text{A}=120^\circ$ and $\text{AB}=\text{AC}$ and given to find $\angle\text{B}$ and $\angle\text{C}.$ We can observe that $\triangle\text{ABC}$ is an isosceles triangle since $\text{AB}=\text{AC}$$\angle\text{B}=\angle\text{C}$ (i)
[Angles opposite to equal sides are equal] We know that sum of angles in a triangle is equal to 180°$\Rightarrow\angle\text{A}+\angle\text{B}+\angle\text{C}=180^\circ$
$\Rightarrow\angle\text{A}+\angle\text{B}+\angle\text{B}=180^\circ$
$\Rightarrow120^\circ+2\angle\text{B}=180^\circ$
$\Rightarrow2\angle\text{B}=180^\circ-120^\circ$
$\Rightarrow\angle\text{B}=\angle\text{C}=30^\circ$
Given Mat $\angle\text{A}=120^\circ$ and $\text{AB}=\text{AC}$ and given to find $\angle\text{B}$ and $\angle\text{C}.$ We can observe that $\triangle\text{ABC}$ is an isosceles triangle since $\text{AB}=\text{AC}$$\angle\text{B}=\angle\text{C}$ (i)[Angles opposite to equal sides are equal] We know that sum of angles in a triangle is equal to 180°$\Rightarrow\angle\text{A}+\angle\text{B}+\angle\text{C}=180^\circ$
$\Rightarrow\angle\text{A}+\angle\text{B}+\angle\text{B}=180^\circ$
$\Rightarrow120^\circ+2\angle\text{B}=180^\circ$
$\Rightarrow2\angle\text{B}=180^\circ-120^\circ$
$\Rightarrow\angle\text{B}=\angle\text{C}=30^\circ$
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