Solution:
Given that
[tex]\theta=155\degree[/tex]
To evaluate the reference angle, we have
[tex]\begin{gathered} \theta+\theta^{\prime}=180(sum\text{ of angles on a line\rparen} \\ \Rightarrow155+\theta^{\prime}=180 \\ add\text{ -155 to both sides} \\ -155+155+\theta^{\prime}=-155+180 \\ \Rightarrow\theta\text{'=25} \end{gathered}[/tex]
Hence, the reference angle is evaluated to be
[tex]25\degree[/tex]
