[cairo] Ellipse stroke

Richard Copley rcopley at gmail.com
Wed Nov 29 20:18:43 UTC 2017

> On the top right and bottom right: avoiding the bug by stroking the
> arc from t to pi-t, where cos²(t) = (r₀² - ∛(r₀r₀L)²) / (r₀² - r₁²),
> where r₀ and r₁ are the ellipse semiaxes and L is the line width.
> (That equation gives the locations of the cusps (if any) in the inner
> curve of the ellipse stroke (proof omitted).)

Typo, sorry. The equation should be:

cos²(t) = (r₀² - ∛(r₀r₁L)²) / (r₀² - r₁²)

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