The perfect Triangle Worksheet is not difficult to find when what is available is organized logically! Here the worksheets are organized by grade level for your convenience. These worksheets will take you and your child from triangle recognition in kindergarten through to establishing missing lengths in congruent triangles. Codman's triangle. Radiology A wedged elevation of periosteum seen on a plain film of the long bones, a 'classic' finding of Ewing sarcoma, also seen in osteosarcoma, bone metastases, hematomas, syphilis, TB. a localized, triangular ridge of new bone formed where periosteum is elevated. A triangle with all interior angles measuring less than 90° is an acute triangle or acute-angled triangle. If c is the length of the longest side, then a 2 + b 2 > c 2, where a and b are the lengths of the other sides. A triangle with one interior angle measuring more than 90° is an obtuse triangle or obtuse-angled triangle. Triangle Patterns. Triangles are known as continuation patterns, meaning the trend stalls out to gather steam before the next breakout or breakdown. They are named triangles as the upper and lower trend line eventually meet to form a tip and connecting the starting points of both trend lines completes a triangle shape.