Hello,

I'm using maple12 and I have a problem with a homework:

restart;
with(plots);
with(DEtools);
eqn := D(y) (x) = sqrt(x^2+y(x)^2);
plot1 := phaseportrait(eqn, y(x), x = -5 .. 5, [[y(0) = 0]], y = -5 .. 5, linecolor = [blue], dirgrid = [30, 30]):
plot2 := implicitplot(x^2+y^2 = 1/4, x = -5 .. 5, y = -2 .. 2, grid = [100, 100], color = green):
plot3 := seq(implicitplot(x^2+y^2 = k^2, x = -5 .. 5, y = -5 .. 5, grid = [100, 100], color = green), k = 1 .. 5);display([plot1, plot2, plot3])