Without using any wolves, show that Robinson’s goat can only graze shapes that are convex (that means, whenever you pick two points inside the shape, the whole line between them also lies inside). But if Robinson is allowed to use as many wolves as he likes, this restriction disappears. Show that in this case, he can make the goat graze in the shape of any polygon at all.
On a field, there are two pegs, \(A\) and \(B\), placed \(15\) metres apart. Each peg has a small ring placed on top, and a rope can slide freely through these rings.
You have one rope and two goats that want to graze the grass - but they will fight each other if they can both reach the same spot. For what lengths of rope can you arrange things so that the goats cannot reach each other?