$$\left( {0,{\pi \over 4}} \right) \cup \left( {{\pi \over 2},{{3\pi } \over 4}} \right) \cup \left( {{{3\pi } \over 2},{{11\pi } \over 6}} \right)$$

$$\left( {0,{\pi \over 2}} \right) \cup \left( {\pi ,{{3\pi } \over 2}} \right)$$

$$\left( {0,{\pi \over 2}} \right) \cup \left( {{\pi \over 2},{{3\pi } \over 4}} \right) \cup \left( {\pi ,{{7\pi } \over 6}} \right)$$

$$\left( {0,{\pi \over 4}} \right) \cup \left( {{\pi \over 2},{{3\pi } \over 4}} \right) \cup \left( {\pi ,{{5\pi } \over 4}} \right) \cup \left( {{{3\pi } \over 2},{{7\pi } \over 4}} \right)$$

has a unique solution if $$\theta \in \left( {{\pi \over 2},{{2\pi } \over 3}} \right)$$ and have infinitely many solutions if $$\theta \in \left( {\pi ,{{7\pi } \over 6}} \right)$$

have infinitely many solutions if $$\theta \in \left( {{\pi \over 2},{{2\pi } \over 3}} \right)$$ and has a unique solution if $$\theta \in \left( {\pi ,{{7\pi } \over 6}} \right)$$

have infinitely many solutions if $$\theta \in \left( {{\pi \over 2},{{2\pi } \over 3}} \right) \cup \left( {\pi ,{{7\pi } \over 6}} \right)$$

has a unique solution if $$\theta \in \left( {{\pi \over 2},{{2\pi } \over 3}} \right) \cup \left( {\pi ,{{7\pi } \over 6}} \right)$$

[2, 6]

[3, 7]

[1, 4]

R

5

3

7

4