% surface_area_increase.m
%
%  A small version of the example in Van Loan 1.1.
%
%  How much does the surface area of a sphere increase if
%  its radius of 6365 is increased by the tiny amount 0.00001?
%
r = 6365
delta = 0.000001
Area = 4 * pi * r^2
Area_plus = 4 * pi * ( r + delta )^2

increase = A_plus - A

