Given: Within many proofs in mathematics, it is important to be able to demonstrate when two mathematical
Given:
Within many proofs in mathematics, it is important to be able to demonstrate when two mathematical statements are logically equivalent to each other. There are a number of statements that are logically equivalent to the following:
The
n
×
n
matrix
A
is invertible.
Ten of these equivalent statements are given below:
• A is an invertible matrix.
• A is row equivalent to the n × n identity matrix.
• A has n pivot positions.
• The equation Ax = 0 has only the trivial solution.
• The equation Ax = b has at least one solution for each b in R n .
• The columns of A span R n .
• The linear transformation x → Ax maps R n onto R n .
• There is an n × n matrix C such that CA = I.
• There is an n × n matrix D such that AD = I.
• The columns of A form a basis of R n .
Task:
Note: It is important that you think critically about your answer to parts A and B, since the remainder of this task depends on the quality of your response to these parts.
-
Provide a definition for logical equivalence.
Note: This definition should be structured so that it can be employed in the parts of the task that follow. - Provide an interpretation for the given statement: The n × n matrix A is invertible.
- Explain what this statement means to you.
C. Write a brief essay ( suggested length of 1–2 pages ) in which you do the following:
-
Justify that the
ten
statements are logically equivalent to the statement "The
n
×
n
matrix
A
is invertible."
Note: Your justification does not need to constitute a formal proof, and you may restrict your arguments to R 2 ( n = 2 ) . For example, you can justify that matrix A has a non-zero determinant by noting that a zero determinant would introduce division by zero in the formula for finding A-1. (Do not use this justification, however, since it was provided as an example.) - Explain how each step in your justifications relates to your answers to parts A and B.
Deliverable: Word Document
