Problem 53 of 7
Prove the exterior angle theorem for triangle ABC with exterior angle at A.
Using a hint is okay. It just tells the trainer to give you a little more review.
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combine linear-pair and triangle-sum relationships.
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Proof must combine a linear pair with the triangle angle sum.
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Your answer is equivalent to the expected form.
Walkthrough
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1. Write the triangle angle-sum equation.
2. Write the linear-pair equation for the exterior angle.
3. Compare or subtract to prove the exterior angle relationship.
Use the worked steps, then substitute the final answer back into the original relationship to confirm it satisfies the prompt.
Circular proof that assumes the exterior angle theorem.