Chapter 6: Problem 16
\(\begin{array}{ll}\text { } & \text { By calculating }(1+1)(\mathbf{v}+\mathbf{w}) \text { in two }\end{array}\) ways (using axioms \(\mathrm{S} 2\) and \(\mathrm{S} 3\) ), show that axiom \(\mathrm{A} 2\) follows from the other axioms.
Short Answer
Expert verified
Axiom A2 follows from axioms S2 and S3 by showing both methods yield \(2\mathbf{v} + 2\mathbf{w}\).
Step by step solution
01
Expand the Expression Using S3 First
First, let's use the axiom S3, which states that scalar multiplication is distributive across vector addition: \[a(\mathbf{v} + \mathbf{w}) = a\mathbf{v} + a\mathbf{w}.\]Applying S3 to our expression, we need to calculate \((1+1)(\mathbf{v}+\mathbf{w})\) by distributing the scalar over the addition:\[(1+1)(\mathbf{v} + \mathbf{w}) = (1+1)\mathbf{v} + (1+1)\mathbf{w}.\]
02
Simplify Using Scalar Arithmetic
Now we simplify using the properties of numbers, specifically that \((1+1) = 2\):\[2\mathbf{v} + 2\mathbf\mathbf{w}.\]
03
Expand the Expression Using S2 First
Apply axiom S2, which describes the addition of scalars:\[(a + b)\mathbf{v} = a\mathbf{v} + b\mathbf{v}.\]Apply this method to our given expression:\[(1+1)(\mathbf{v}+\mathbf{w}) = 1(\mathbf{v}+\mathbf{w}) + 1(\mathbf{v}+\mathbf{w}).\]
04
Distribute Each Term Individually Using S3
Now, apply S3 to each term in the expression separately:\[= 1\mathbf{v} + 1\mathbf{w} + 1\mathbf{v} + 1\mathbf{w}.\]
05
Combine Like Terms
Combine like terms:\[= (1\mathbf{v} + 1\mathbf{v}) + (1\mathbf{w} + 1\mathbf{w}).\]This simplifies to:\[= 2\mathbf{v} + 2\mathbf{w}.\]
06
Show Equivalence to Prove A2
Since both methods of calculation result in \(2\mathbf{v} + 2\mathbf{w}\), we have shown that using the axioms S2 and S3 implies the distributivity of the scalar multiplication over the vector sum in a manner that verifies A2. Hence axiom A2, which states that \((a+b)\mathbf{v} = a\mathbf{v} + b\mathbf{v}\), follows from axioms S2 and S3.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Scalar Multiplication
In vector calculus, scalar multiplication is an operation that involves multiplying a vector by a scalar (a real number). This operation is fundamental because it alters the magnitude of the vector without changing its direction, unless the scalar is negative, which reverses the vector's direction.
- To multiply a vector by a scalar, you multiply each component of the vector by that scalar.
- If the vector is \( \mathbf{v} = [v_1, v_2, v_3] \) and the scalar is \( a \), then \( a\mathbf{v} = [a \cdot v_1, a \cdot v_2, a \cdot v_3] \).
Vector Addition
Vector addition is another key concept in vector calculus. It involves combining two or more vectors to produce a resultant vector. This operation is performed by adding the corresponding components of the vectors involved.
When adding two vectors \( \mathbf{v} = [v_1, v_2, v_3] \) and \( \mathbf{w} = [w_1, w_2, w_3] \), the result is a new vector:
When adding two vectors \( \mathbf{v} = [v_1, v_2, v_3] \) and \( \mathbf{w} = [w_1, w_2, w_3] \), the result is a new vector:
- \( \mathbf{v} + \mathbf{w} = [v_1 + w_1, v_2 + w_2, v_3 + w_3] \).
Distributive Property
The distributive property is a fascinating principle that connects scalar multiplication with vector addition. It states that multiplying a scalar with a sum of vectors can be done by distributing the scalar multiplication over each vector individually.
Mathematically, for a scalar \( a \) and vectors \( \mathbf{v} \) and \( \mathbf{w} \), it is expressed as:
Mathematically, for a scalar \( a \) and vectors \( \mathbf{v} \) and \( \mathbf{w} \), it is expressed as:
- \( a(\mathbf{v} + \mathbf{w}) = a\mathbf{v} + a\mathbf{w} \).