7: Parallel Lines Last updated Sep 5, 2021 Save as PDF 6.4: Ptolemy's inequality 7.1: Parallel lines Page ID23625 Anton PetruninPennsylvannia State University ( \newcommand{\kernel}{\mathrm{null}\,}\) 7.1: Parallel lines7.2: Reflection Across a Point7.3: Transversal Property7.4: Angles of triangles7.5: Parallelograms7.6: Method of coordinates7.7: Apollonian Circle