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boya's Question
Math
Posted 9 months ago

24. (T/F) Not every orthogonal set in Rn\mathbb{R}^{n} is linearly independent.
25. (T/F) If y\mathbf{y} is a linear combination of nonzero vectors from an orthogonal set, then the weights in the linear combination can be computed without row operations on a matrix.
26. (T/F) If a set S={u1,,up}S=\left\{\mathbf{u}_{1}, \ldots, \mathbf{u}_{p}\right\} has the property that uiuj=0\mathbf{u}_{i} \cdot \mathbf{u}_{j}=0 whenever iji \neq j, then SS is an orthonormal set.
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Answer from Sia
Posted 9 months ago
Solution by Steps
step 1
Identify the statement: "Not every orthogonal set in Rn\mathbb{R}^{n} is linearly independent."
step 2
Recall the definition of an orthogonal set: A set of vectors {u1,u2,,up}\{\mathbf{u}_1, \mathbf{u}_2, \ldots, \mathbf{u}_p\} is orthogonal if uiuj=0\mathbf{u}_i \cdot \mathbf{u}_j = 0 for all iji \neq j
step 3
Recall the property of orthogonal sets: In Rn\mathbb{R}^{n}, any orthogonal set of nonzero vectors is linearly independent
step 4
Conclude that the statement is False because every orthogonal set of nonzero vectors in Rn\mathbb{R}^{n} is linearly independent
Answer
False
Key Concept
Orthogonal sets and linear independence
Explanation
In Rn\mathbb{R}^{n}, any orthogonal set of nonzero vectors is always linearly independent.


 Question 25
step 1
Identify the statement: "If y\mathbf{y} is a linear combination of nonzero vectors from an orthogonal set, then the weights in the linear combination can be computed without row operations on a matrix."
step 2
Recall the property of orthogonal sets: If {u1,u2,,up}\{\mathbf{u}_1, \mathbf{u}_2, \ldots, \mathbf{u}_p\} is an orthogonal set, then any vector y\mathbf{y} that is a linear combination of these vectors can be written as y=c1u1+c2u2++cpup\mathbf{y} = c_1 \mathbf{u}_1 + c_2 \mathbf{u}_2 + \ldots + c_p \mathbf{u}_p
step 3
The weights cic_i can be computed using the formula ci=yuiuiuic_i = \frac{\mathbf{y} \cdot \mathbf{u}_i}{\mathbf{u}_i \cdot \mathbf{u}_i}, which does not require row operations on a matrix
step 4
Conclude that the statement is True because the weights can be computed directly using the dot product
Answer
True
Key Concept
Weights in linear combinations of orthogonal sets
Explanation
The weights in the linear combination of vectors from an orthogonal set can be computed directly using dot products, without the need for row operations on a matrix.


 Question 26
step 1
Identify the statement: "If a set S={u1,,up}S=\left\{\mathbf{u}_1, \ldots, \mathbf{u}_p\right\} has the property that uiuj=0\mathbf{u}_i \cdot \mathbf{u}_j=0 whenever iji \neq j, then SS is an orthonormal set."
step 2
Recall the definition of an orthonormal set: A set of vectors {u1,u2,,up}\{\mathbf{u}_1, \mathbf{u}_2, \ldots, \mathbf{u}_p\} is orthonormal if uiuj=0\mathbf{u}_i \cdot \mathbf{u}_j = 0 for all iji \neq j and ui=1\|\mathbf{u}_i\| = 1 for all ii
step 3
Note that the given property uiuj=0\mathbf{u}_i \cdot \mathbf{u}_j=0 for iji \neq j only ensures orthogonality, not orthonormality
step 4
Conclude that the statement is False because orthonormality also requires each vector to have a unit norm, which is not guaranteed by orthogonality alone
Answer
False
Key Concept
Orthogonal vs. Orthonormal sets
Explanation
An orthonormal set requires both orthogonality and unit norm for each vector, whereas the given property only ensures orthogonality.

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