Jigsawing a quadrangle from a triangle - Floor van Lamoen For an acute-angled triangle ABC, we construct two isotomic points P and Q on BC and P' and Q' on AB and AC respectively, such that BPP' and CQQ' are right triangles which, when rotated about P' and Q' respectively through appropriate angles fit with AP'Q' to a quadrangle with a new fourth vertex A'. We show that AA' passes trough the circumcenter O. ✪ ✪ ✪ ✪ ✪ Link tải tài liệu: LINK TẢI TÀI LIỆU Theo LTTK Education