[tex]\frac{5\pi }{4}[/tex] or [tex]\frac{7\pi }{4}[/tex]
divide both sides by 2
sinΘ = - [tex]\frac{\sqrt{2} }{2}[/tex]
Since the sin ratio is negative then Θ is in third / fourth quadrants
Θ = [tex]sin^{- 1}[/tex] ([tex]\frac{\sqrt{2} }{2}[/tex]) = [tex]\frac{\pi }{4}[/tex] related acute angle
Θ = ( π + [tex]\frac{\pi }{4}[/tex] ) = [tex]\frac{5\pi }{4}[/tex]
or Θ = ( 2π - [tex]\frac{\pi }{4}[/tex] ) = [tex]\frac{7\pi }{4}[/tex]
