Question

What is the measure of the third angle of a triangle if the measure of the two angles are $45°$ and $123°$?

Answer 1

Given: Two angle of the triangle are $45°$ and $123°$.

Let the third angle of a triangle is $\mathrm{a}$.

We know that the sum of the all interior angle of the triangle is $180°$.

Thus,

$$\begin{gathered} 45°+123°+\mathrm{a}=180° \\ \Rightarrow 168°+\mathrm{a}=180° \\ \Rightarrow \mathrm{a}=180°-168° \\ \Rightarrow \mathrm{a}=12° \end{gathered}$$

Hence, the third angle of the triangle is $12°$.