Every geometry proof is a sequence of deductions that use if-then logic.
You write one of the given facts as statement 1. Then, for statement 2, you put something that follows from statement 1 and write your justification for that in the reason column.
Then you proceed to statement 3, and so on, till you get to the prove statement.
The way you get from statement 1 to statement 2, from statement 2 to statement 3, and so on is by using if-then logic.
A two-column geometry proof is in essence a logical argument or a chain of logical deductions, like
If I study, then I’ll get good grades.
If I get good grades, then I’ll get into a good college.
If I get into a good college, then I’ll become a babe/guy magnet.
(And so on . . .)
(Except that geometry proofs are about geometric figures, naturally.)
Note that each of these steps is a sentence with an if clause and a then clause.
From Logic for Dummies
Philosophy 103: Introduction
to Logic
Philosophy 103: Introduction to Logic
Conditional Statements and Material Implication
In logic, a conditional is a compound statement formed by combining two sentences (or facts) using the words "if ... then." A conditional can also be called an implication.
Wikipedia on Conditional Statements
