Lesson 4
1. Lesson 4
Module 2: Logic and Geometry
Lesson 4: Identifying Errors in Proofs
Focus
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Many types of puzzles or problems involve the use of reasoning to solve a mystery. TV shows like CSI or NCIS often have the lead detectives make a conjecture about the identity of the murderer and then justify their reasoning through investigation.
Not all reasoning used to justify a proof is valid. For instance, circumstantial evidence often points at one suspect and, often times, once the forensic analysis is done, a different suspect is identified.
This lesson will help you answer the following inquiry question:
- How can the validity of a proof be justified?
Assessment
- Lesson 4 Assignment
All assessment items you encounter need to be placed in your course folder.

Save a copy of the Lesson 4 Assignment to your course folder. You will receive more information about how to complete the assignment later in this lesson.