= Krivine rounding scheme
{c}
For a bipartite <elliptope> <matrix> $X$, put $t=\log(1+\sqrt2)$ and apply $\sinh(tx)$ within the two diagonal blocks and $\sin(tx)$ across them. Matching absolute <power series> <coefficients> give a <positive semidefinite matrix> by <coefficient-dominated entrywise positivity>, while $\sinh t=1$ gives unit diagonal. <Gaussian hyperplane rounding> then turns each cross-block <correlation coefficient> into $(2/\pi)\arcsin(\sin(tX_{ij}))=(2t/\pi)X_{ij}$ because $t<\pi/2$. The zero diagonal blocks of the bipartite objective eliminate every other contribution.
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