Octave tasks from classwork.

Task 1

p = [1 -3 2];
r = roots(p);
x = linspace(-1, 3);
plot(x, polyval(p, x));
hold on;
plot(r, zeros(size(r)), "marker", "x", "markersize", 21, "color", "red", "linestyle", "none")
hold on;
plot(x, zeros(size(x)), '.', 'color', 'red');

Task 2

x = y = linspace(-360, 360, 26);
[xx, yy] = meshgrid (x, y);
z = sin(xx .* yy);
surf(xx, yy, z);

Task 3

%# x = y = linspace(-360, 360, 10)

%# x = y = 0.2:10;

x = y = linspace(0.2, 10, 100);

r = sqrt(x .^ 2 + y .^ 2);

[xx, yy] = meshgrid(x, y);
%# u = 1/(r .^ 12) - 1/(r .^ 6);
%# surf(xx, yy, u);
u = 1 ./ (r .^ 12) - 1 ./ (r .^ 6);
plot(r, u);