Respuesta :

With [tex]\theta[/tex] in quadrant II, we expect to have [tex]\cos\theta<0[/tex]. Then

[tex]\cos^2\theta+\sin^2\theta=1\implies\cos\theta=-\sqrt{1-\sin^2\theta}[/tex]

[tex]\implies\cos\theta=-\dfrac{\sqrt3}2[/tex]