Hi

This is a three-part question:

a. the graph y = f(x) in the xy-plane has parametrization x=x, y=f(x), and vector formula r(x) = xi + f(x)j. Use this to show that if f is twice-differentiable, then

((absvalue f''(x))/[1+((f'(x))^2]^3/2

b. use the formula for k in part a to find the curvature of y = ln(cosx) when -pi/2 < x < pi/2.

c. show that the curvature is zero at the point of inflection.