Contents:
1.x.x - triangles
2.x.x - lines

x.0.x - angles
x.1.x - line segments
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Number - Name - Description
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1.0.1 - Triangle Sum Theorem - All angles in a triangle add up to 180 degrees
2.0.1 - Straight Angle Theorem - Any components of a straight angle are supplementary
2.1.1 - Subsegment Sum Theorem - All parts of a line segment sum to the whole segment