Orthic quadrilaterals of a convex quadrilateral - Maria Flavia Mammana, Biagio Micale and Mario Pennisi We introduce the orthic quadrilaterals of a convex quadrilateral, based on the notion of valtitudes. These orthic quadrilaterals have properties analogous to those of the orthic triangle of a triangle. ✪ ✪ ✪ ✪ ✪ Link tải tài liệu: LINK TẢI TÀI LIỆU Theo LTTK Education