Error Analysis B

Khan Academy video wrapper

Consider the following diagram where

\overset{―}{A B} ≅ \overset{―}{B C}

and

\overset{―}{A D} ≅ \overset{―}{D C}

Here is Max's proof that

\overset{―}{B D}

bisects

∠ A B C

Step	Statement	Reason
1	$\overset{―}{A B} ≅ \overset{―}{B C}$ ‍	Given
2	$\overset{―}{A D} ≅ \overset{―}{D C}$ ‍	Given
3	$△ A B D ≅ △ B D C$ ‍	Side-side-side $≅$ ‍
4	$∠ A B D ≅ ∠ D B C$ ‍	Corresponding angles in congruent triangles
5	$\overset{―}{B D}$ ‍ bisects $∠ A B C$ ‍	$∠ A B D ≅ ∠ D B C$ ‍

Max first made a mistake in step

because

Consider the following diagram where

\overset{―}{B G} ≅ \overset{―}{G D}

and

\overset{―}{I G} ≅ \overset{―}{G O}

Here is Sunil's proof that

△ B G I ≅ △ D G O

Where is the first step that Sunil made a mistake in his proof?

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