$3\text{-sphere}$ |
|
$=$ |
|
$\partial(4\text{-ball})$ |
|
|
$\approx$ |
|
$\partial({\rm hypercube})$ |
|
|
$=$ |
|
$\partial(\square\times\square)$ |
|
|
$=$ |
|
$(\box\times\square)\cup(\square\times\box)$ |
|
|
$\approx$ |
|
$(\circle\times\disc)\cup(\disc\times\circle)$ |
|
|
$=$ |
|
Solid Torus $+$ Solid Torus |