Visual Walkthrough: How to Complete Every Gina Wilson Segment Proof Step by Step
Q1: Why can't I just say $AB + BC = AC$ is the "Definition of Between"?
A1: In standard Euclidean geometry and specifically within the Gina Wilson curriculum, the relationship where adjacent collinear parts combine to form a whole is officially defined as the Segment Addition Postulate. "Betweenness" simply states that point $B$ lies somewhere along the path between $A$ and $C$, but the formal algebraic equation ($AB + BC = AC$) requires citing the postulate.
Q2: When should I use Reflexive Property in segment proofs?
A2: Use the Reflexive Property ($XY = XY$ or $\overline{XY} \cong \overline{XY}$) whenever two distinct segments share a common middle segment. Showing that this shared middle piece is equal to itself allows you to add it to both sides of an equation without changing their underlying balance.
Q3: How do I know whether to write "Definition of Congruence" or "Substitution"?
A3: Look at the mathematical symbols changing on the page. If the only change between steps is converting a congruence symbol ($\cong$) with segment bars to an equal sign ($=$) without bars, the reason is the Definition of Congruence. If you are replacing a segment name inside an existing addition or subtraction equation with an equal segment, the reason is Substitution.
Q4: Why does Gina Wilson introduce algebraic proofs before segment proofs?
A4: Wilson structures Unit 2 this way to lower the cognitive load on students. Justifying standard algebra steps (such as the Subtraction Property of Equality or Distributive Property) teaches the formal two-column format using familiar arithmetic rules before introducing abstract geometric postulates.