sin230° cos245° - 3 sin2 30° + 2 cos2 90°
= \((\frac{1}{2})^2 (\frac{1}{\sqrt2})^2 \) - 3 \((\frac{1}{2})^2\) + 2 (0)2
= \(\frac{1}{4} \times \frac{1}{2}\) - 3 x \(\frac{1}{4}\) + 0
= \(\frac{1}{8}\) - \(\frac{3}{4}\)
= \(\frac{1-3}{8}\)
= \(\frac{-2}{8}\)
= \(\frac{-1}{4}\)