An astroid looks like a
rhombus with sides slightly curved in towards the center.
To plot astroid use the following
parametric equations:
x = a *
cos(Q)
^ 3
y = a *
sin(Q) ^ 3
In case you're curious, the
area will be equal to 3
Pi*a^2/8. (You can verify that by
integrating the aforemetioned equation from 0 to Pi/2 and then multiplying by 4 (it's
symmetric)).
To plot in MapleV use the following command:
plot([4*cos(x)^3,4*sin(x)^3,x=0..2*Pi]);