x = linspace ( 0, 10, 101 );
z = 0.5 * ( x - 3.5 ).^2 + 12 + 0.1 * ( x - 2 ) .* ( x - 5 ) .* ( x - 8 );
h1 = plot ( x, z, 'b-' );
set ( h1, 'LineWidth', 2 );
axis ( [ 0, 10, 0, 45 ] )
hold on
pause

y = 0.5 * ( x - 3.5 ).^2 + 12;
x3 = [ x(21), x(51), x(81) ];
y3 = [ y(21), y(51), y(81) ];
h2 = plot ( x3, y3, 'k.' );
set ( h2, 'MarkerSize', 30.0 )
pause

h3 = plot ( x, y, 'r' );
set ( h3, 'LineWidth', 2.0 )
pause

x2 = [ x, 10, 0 ];
y2 = [ y, 0, 0 ];
fill ( x2, y2, 'y' )
h4 = plot ( x, z, 'b-' );
set ( h4, 'LineWidth', 2 )
pause
clf

