J0 = @(x) besselj ( 0, x );      % <- a “one line” function;
for n = 0 : 10
  z(n) = fzero ( J0, [ (n-1)*pi, n*pi] );
end
x = linspace ( 0.0, 10.0*pi, 501 );
y = J0(x);
plot ( x, y, ‘-’, ...
         x, 0*y, ‘k:’, ...
         z, zeros ( 1, 10 ), ‘o’, ...
         ‘LineWidth’, 3, ‘Markersize’, 50 );
axis ( [ 0.0, 10.0 * pi, -0.5, 1.0 ] );
