The first step of an indirect proof is to assume the opposite, or negation, of the given statement.
Assume temporarily that XB ≠≅ XA.
Practice makes perfect
The first step of an indirect proof is to assume the opposite, or negation, of the given statement. Let's think about the second part of the given statement.
XB ≅ XA
To write a negation of this statement, we need to consider how to say its opposite. Here we can do this by negating the congruence symbol.
Negation: & XB 4pt ≠≅ XA
Since the first step is to temporarily assume the opposite, we should include this fact in our sentence.
First step:
Assume temporarily thatXB 4pt ≠≅ XA.
