The first step of an indirect proof is to assume the opposite, or negation, of the given statement.
Assume temporarily that m∠2 ≤ 90.
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 given statement.
m∠2 > 90
To write a negation of the given statement, we need to consider how to say its opposite. We will negate this statement by changing the > symbol into the ≤ symbol.
Negation: & m∠2 ≤ 90
Since the first step is to temporarily assume the opposite, we should include this fact in our sentence.
First step:
Assume temporarily that m∠2 ≤ 90.
