The definition is, X unknots in Y if any two embeddings are equivalent. How do you show $S^{1}$ unknots in $\mathbb{R}^{4}$ and in general, $S^{n}$ unknots or knots in $\mathbb{R}^{m}$?
The solution given is： The cone C(S1) in S1 in in general position is non-singular, hence we can perform a sequence of cellular moves across triangles to move s1 to the boundary of a triangle. It's easy to see that any two linear embeddings of triangles are equivalent.
Can someone explain the solution?