Question

In a triangle, if one angle measures $40°$ and the other two angles are equal, find their measures.

Answer 1

We have a triangle , whose one angle = ${40}^{\circ }$

The other two angles are equal and equal to $x^{\circ }$ (let)

Sum of all interior angles of triangle = ${180}^{\circ }$

$$\begin{gathered} \Rightarrow x^{\circ }+x^{\circ }+{40}^{\circ }={180}^{\circ } \\ \Rightarrow 2x+40=180 \\ \Rightarrow 2x=180-40 \\ \Rightarrow 2x=140 \\ \Rightarrow x=\frac{140}{2}=70 \\ \Rightarrow x={70}^{\circ } \end{gathered}$$

Hence, the required equal angles are ${70}^{\circ }$.