Sudut-sudut yang bukan sudut istimewa dicari hubungannya dengan menggunakan relasi sudut.
Contoh 1
Tentukan nilai eksak dari \(\dfrac{\sin 20^{\text{o}}}{\cos 110^{\text{o}}}\)
\begin{equation*}
\begin{split}
& \frac{\sin 20^{\text{o}}}{\cos 110^{\text{o}}} \\\\
& \frac{\sin 20^{\text{o}}}{\cos (90^{\text{o}} + 20^{\text{o}})} \\\\
& \frac{\sin 20^{\text{o}}}{- \sin 20^{\text{o}}} \\\\
& -1
\end{split}
\end{equation*}
Contoh 2
Tentukan nilai eksak dari \( \tan 156^{\text{o}} \;.\: \dfrac{\cos 336^{\text{o}}}{\sin 204^{\text{o}}}\)
\begin{equation*}
\begin{split}
& \tan 156^{\text{o}} \;.\: \frac{\cos 336^{\text{o}}}{\sin 204^{\text{o}}} \\\\
& \frac {\sin 156^{\text{o}}}{\cos 156^{\text{o}}} \;.\: \frac{\cos 336^{\text{o}}}{\sin 204^{\text{o}}} \\\\
& \frac {\sin (180^{\text{o}} - 24^{\text{o}})}{\cos (180^{\text{o}} - 24^{\text{o}})} \:.\: \frac{\cos (360^{\text{o}} - 24^{\text{o}})}{\sin (180^{\text{o}} + 24^{\text{o}})} \\\\
& \frac {\sin 24^{\text{o}}}{-\cos 24^{\text{o}}} \;.\: \frac{\cos 24^{\text{o}}}{- \sin 24^{\text{o}}} \\\\
& 1
\end{split}
\end{equation*}