{{{id=1| x=var('x') a=3 #LET US SUPPOSE e=2/a b=sqrt(a^2*(1-e^2)) y=sqrt(b^2*(1-x^2/a^2)) plot(y,(x,-a,a),color="blue")+plot(-y,(x,-a,a),color="blue") ///

}}} {{{id=2| /// }}} {{{id=3| /// }}}