1. The graph below shows the curve with equation $y=2sin \theta$, in the interval  $0^{\circ}\leq \theta \leq360^{\circ}$. One value of $\theta$ has been labelled $( \theta =a^{\circ})$.

Use the graph, along with the symmetry properties of the sine function, to verify that 

                              $2sina=2sin(180^{\circ}-a)=-2sin(180^{\circ}+a)=-2sin(360^{\circ}-a)$.