The first step of an indirect proof is to assume the opposite, or negation, of the given statement.
Assume temporarily that no two angles of â–ł PQR are congruent.
Practice makes perfect
The first step of an indirect proof is to assume the opposite, or negate the statement. Let's think about the given statement.
â–ł PQR has two congruent angles.
To negate a statement, we need to consider how to say the opposite. Typically this can be done using the word not. Here, though, it will be more natural to state that No two angles are congruent.
Negation: & No two angles ofâ–ł PQR & are congruent.
Since the first step is to temporarily assume the opposite, we should include this fact in our sentence.
First step: & Assume temporarily no two & angles ofâ–ł PQR are congruent.
