Trigonometry, 2ADV EQ-Bank 3 Find the exact value of \(\cos \left(-150^{\circ}\right)\) (1 mark) --- 3 WORK AREA LINES (style=lined) --- \(\sin \, 585^{\circ}\) (1 mark) --- 3 WORK AREA LINES (style=lined) --- Show Answers Only a. \(-\dfrac{\sqrt{3}}{2}\) b. \(-\dfrac{1}{\sqrt{2}}\) Show Worked Solution a. \(\cos \left(-150^{\circ}\right)=\cos 210^{\circ}\) \(\cos 210^{\circ}=\cos (180+30)=-\cos 30^{\circ}=-\dfrac{\sqrt{3}}{2}\) b. \(\sin 585^{\circ}=\sin 225^{\circ}\) \(\sin 225^{\circ}=\sin (180+45)=-\sin 45^{\circ}=-\dfrac{1}{\sqrt{2}}\)