Figure-eight knot group
= Figure-eight knot group
{title2=$\langle a,b\mid ab^{-1}a^{-1}ba=bab^{-1}a^{-1}b\rangle$}
The <fundamental group> of the <figure-eight knot> complement has the displayed two-generator one-relator presentation. It follows from the <Artin automorphism of a braid> for $(\sigma_1\sigma_2^{-1})^2$ by eliminating the third meridian from its fixed-generator presentation.