Final answer:
Yes, a summary of a writing, recording, or photograph can be used as secondary evidence to prove the content of the original if the original is unavailable.
Step-by-step explanation:
Yes, a summary of a writing, recording, or photograph can be used as secondary evidence to prove the content of the original if the original is unavailable. Secondary sources, such as summaries, provide an interpretation or commentary on primary sources, which are the original documents or records. While primary sources are considered the best possible resource for historians, secondary sources can still be valuable in supporting arguments or providing additional context.