Find the value of $\sin ^2 60^{\circ}+\cos ^2 30^{\circ}-\sin ^2 45^{\circ}-3 \sin ^2 90^{\circ}$.

$\frac{1}{3}$ $-1 \frac{3}{4}$ $-2 \frac{1}{2}$ -2

-2

sin²60º + cos²30º - sin²45º - 3sin²90º = \(\frac{3}{4}\) + \(\frac{3}{4}\) - \(\frac{1}{2}\) - 3 = 1 - 3 = -2