Answer
\[\,\,\theta = 0,\pi ,\frac{\pi }{2},\frac{{3\pi }}{2}\,\,\]
Work Step by Step
\[\begin{gathered}
\sin \theta \cos \theta = 0\, \hfill \\
\, \hfill \\
so\,\,\sin \theta = 0\,\,or\,\,\cos \theta = 0 \hfill \\
\hfill \\
Using\,\,figure\,\,1.63\,\,and\,\,the\,definition\,of\,\,sine\,and\,\,cosine \hfill \\
\,functions\,we\,obtain. \hfill \\
\hfill \\
If\,\,\sin \,\theta = 0\,\,\,then\,\,\theta = 0,\pi \hfill \\
\hfill \\
If\,\,\cos \theta \, = 0\,\,\,\,Then\,\,\,\,\theta = \frac{\pi }{2}\,,\,\frac{{3\pi }}{2} \hfill \\
\hfill \\
{\text{Therefore}} \hfill \\
\hfill \\
All\,solutions\,\,are\,\,:\,\,\,\theta = 0,\pi ,\frac{\pi }{2},\frac{{3\pi }}{2}\,\, \hfill \\
\end{gathered} \]
