An indirect proof starts with the assumption that the statement we are trying to prove is not true.
∠1 and ∠2 are supplementary angles.
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An indirect proof starts with the assumption that the statement we are trying to prove is not true.
In this case, the statement is that ∠1 and ∠2 are notsupplementary angles.
The negation of this statement is that the angles are supplementary angles.
∠1and∠2 are notsupplementary angles.
⇓
∠1and∠2 aresupplementary angles.
Finally, we can state the assumption we would make to start the indirect proof.
Assumption:
∠1 and ∠2 are supplementary angles.
