Step-by-step explanation:
[tex]\cos 90 \cos 30 + \sec^2 45 \sin 30 - \cos 270 \sin 180[/tex]
But we know that
[tex]\cos 90 = \cos 270 = \sin 180 = 0[/tex]
and
[tex]\sin 30 = \dfrac{\sqrt{3}}{2} \:\:\text{and}\:\: \sec 45 = \sqrt{2}[/tex]
so this leaves us with just
[tex]\sec^2 45 \sin 30 = (\sqrt{2})^2 \left(\dfrac{\sqrt{3}}{2} \right)= \sqrt{3}[/tex]
