nsvg__sqr
d = nsvg__sqr(x1p)/nsvg__sqr(rx) + nsvg__sqr(y1p)/nsvg__sqr(ry);
sa = nsvg__sqr(rx)*nsvg__sqr(ry) - nsvg__sqr(rx)*nsvg__sqr(y1p) - nsvg__sqr(ry)*nsvg__sqr(x1p);
sb = nsvg__sqr(rx)*nsvg__sqr(y1p) + nsvg__sqr(ry)*nsvg__sqr(x1p);