Let (A2,\documentclass[12pt]{minimal}
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\begin{document}$ \mathcal{C} $\end{document}) be a Minkowski plane with a centrally symmetric, strictly convex C1-curve \documentclass[12pt]{minimal}
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\begin{document}$ \mathcal{C} $\end{document} as the unit circle. Then \documentclass[12pt]{minimal}
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\begin{document}$ \mathcal{C} $\end{document} induces in (A2,\documentclass[12pt]{minimal}
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\begin{document}$ \mathcal{C} $\end{document}) a left-orthogonality structure '\documentclass[12pt]{minimal}
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\begin{document}$ \dashv $\end{document}' by setting tangents of \documentclass[12pt]{minimal}
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\begin{document}$ \mathcal{C} $\end{document} (and their parallels) left-orthogonal to the corresponding radii (and their paralles). If a line g is left-orthogonal to another one h, then h is right-orthogonal to \documentclass[12pt]{minimal}
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\begin{document}$ g, (h \vdash g) $\end{document}. Based on those concepts of orthogonality in (A2,
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\begin{document}$ \mathcal{C} $\end{document}) left- and right-altitudes of a triangle are defined and one can discuss the existence of left- or right-orthocentric triangles. In general Minkowski planes these concepts of orthocenters are independent of a third type of a triangle-orthocenter, which is based on a circle-geometric definition due to Asplund and Grünbaum, c.f. [1].¶¶Further results are the following: In every plane A2,\documentclass[12pt]{minimal}
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\begin{document}$ \mathcal{C} $\end{document} there exist triplets of directions \documentclass[12pt]{minimal}
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\begin{document}$ \overline{g}_i $\end{document} such that the triangles \documentclass[12pt]{minimal}
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\begin{document}$ \mathcal {T} $\end{document} having sides gi parallel to \documentclass[12pt]{minimal}
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\begin{document}$ \overline{g}_i $\end{document} are left-orthocentric. A plane A2,\documentclass[12pt]{minimal}
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\begin{document}$ \mathcal{C} $\end{document} is euclidean, iff each triangle \documentclass[12pt]{minimal}
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\begin{document}$ \mathcal {T} $\end{document} is left-orthocentric. Constructing the altitudes of an altitude-triangle of a non (left- or right-)-orthocentric triangle \documentclass[12pt]{minimal}
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\begin{document}$ \mathcal {T} $\end{document} starts iteration processes with attractors (resp. repulsors) which can be called ‘limit orthocenters’ to the given triangle \documentclass[12pt]{minimal}
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\begin{document}$ \mathcal {T} $\end{document}.
