5. Find the equation of the tangent line to the graph of f(a) = -sec(a) at the point (0, -1)
6. Differentiate y = sin(x)tan(x).
7. Find f '(x) for f(x) = sin(x)cot(x).
8. Find the derivative of the function f(x) = cos^2(x) + tan^2(x)
9. Find f '(x) for f(x) = xln(x) - 5ex.