% Calculates the increase in surface area of a sphere using two formulas,
% given the original radius and the amount by which it is increased

r=input('Enter the original radius (in meters): ');
inc_r=input('Enter the radius increment (also in meters): ');
disp('Surface area increase:')

% Method 1
incA1 = 4*pi*(r+inc_r)^2-4*pi*r^2;
fprintf('  First formula:  %15.6f square meters\n', incA1)

% Method 2
incA2 = 4*pi*(2*r+inc_r)*inc_r;
fprintf('  Second formula: %15.6f square meters\n', incA2)