Angles With Parallel Sides Small 310×320 Medium 621×640 Large 993×1024 Download TIFF Original 2910×3000 | (149.8 KB) Description Illustration of angles with parallel sides. "GH is parallel to and lies in the same direction as DE, and HI is parallel to but lies in the opposite direction to EF; hence, angle GHI is the supplement of DEF." Keywords angle, parallel sides of angles, supplement, supplementary Galleries Miscellaneous Angles Source: International Correspondence Schools I.C.S. Reference Library Mathematics (Scranton: International Textbook Company, 1905) Geometry & Trigonometry Pg. 6