evaluate tan^2(4pi/3)- Sec^2(-11pi/6)
$$\\ tan^2(4pi/3)- Sec^2(-11pi/6)\\\\ =tan^2(pi/3)- Sec^2(pi/6)\\\\ =(\sqrt3)^2-(\frac{2}{\sqrt3})^2\\\\ =3-\frac{4}{3}\\\\ =\frac{9-4}{3}\\\\ =\frac{5}{3}\\\\$$