Question

For the triangle shown in the picture two angles are given find the third angle without using a protractor.

Answer 1

Let's use x for the missing angle. The sum of the internal angles of a triangle is equal to 180°. Then we have:

`\begin{gathered} 180^(\circ)=x+29^(\circ)+109^(\circ)=x+138^(\circ) \\ 180^(\circ)=x+138^(\circ) \end{gathered}`

Then if we substract 138° from both sides we get:

`\begin{gathered} 180^(\circ)-138^(\circ)^{}=x+138^(\circ)-138^(\circ) \\ x=42^(\circ) \end{gathered}`

Then the answer is 42°.