Let f(x)=secx for x measured in radians.
A point P lies on the graph of f at x=4π.
a. Calculate f′(4π). Show all necessary algebraic work.
b. Write an explicit equation for the tangent line to the graph of f at point P. Express the equation in point–slope form.
c. Determine the equation of the line normal to the graph of f at point P. Express the equation in slope–intercept form.