5: Perpendicular lines Last updated Sep 5, 2021 Save as PDF 4.5: On side-side-angle and side-angle-angle 5.1: Right, Acute and Obtuse Angles Page ID23611 Anton PetruninPennsylvannia State University ( \newcommand{\kernel}{\mathrm{null}\,}\) 5.1: Right, Acute and Obtuse Angles5.2: Perpendicular Bisector5.3: Uniqueness of a perpendicular5.4: Reflection across a line5.5: Perpendicular is shortest5.6: Circles5.7: Geometric constructions