3 Intersecting Planes Small 269×320 Medium 538×640 Large 860×1024 Download TIFF Original 2016×2400 | (393.2 KB) Description Illustration of three intersecting planes. "The straight line perpendicular to one of two parallel lanes is perpendicular to the other." Keywords intersection, parallels, perpendicular, plane Galleries Geometric Theorems and Proofs Source: Arthur Latham Baker The Elements of Solid Geometr with Numerous Exercises (Boston, MA: Ginn & Company, 1893)