Textbook Question
In Exercises 37–39, find the dot product v ⋅ w. Then find the angle between v and w to the nearest tenth of a degree.
v = 2i + 4j, w = 6i - 11j
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8. Vectors
Dot Product
1:51 minutesProblem 49
Textbook Question
In Exercises 45–50, determine whether v and w are parallel, orthogonal, or neither. v = 3i - 5j, w = 6i + 18 j 5
Verified step by step guidance1
Identify the vectors \( \mathbf{v} = 3\mathbf{i} - 5\mathbf{j} \) and \( \mathbf{w} = 6\mathbf{i} + 18\mathbf{j} \). Write them in component form as \( \mathbf{v} = (3, -5) \) and \( \mathbf{w} = (6, 18) \).
To check if the vectors are parallel, see if one vector is a scalar multiple of the other. This means checking if there exists a scalar \( k \) such that \( (6, 18) = k(3, -5) \).
To check if the vectors are orthogonal (perpendicular), calculate their dot product using the formula \( \mathbf{v} \cdot \mathbf{w} = v_1 w_1 + v_2 w_2 \). If the dot product equals zero, the vectors are orthogonal.
Calculate the dot product \( \mathbf{v} \cdot \mathbf{w} = 3 \times 6 + (-5) \times 18 \).
Based on the results from the scalar multiple check and the dot product, conclude whether \( \mathbf{v} \) and \( \mathbf{w} \) are parallel, orthogonal, or neither.
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Video duration:
1mKey Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Vector Representation in Component Form
Vectors can be expressed in terms of their components along the coordinate axes, such as v = 3i - 5j, where i and j are unit vectors along the x and y axes. Understanding this form allows for straightforward calculation of vector operations like dot product and scalar multiplication.
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Parallel Vectors
Two vectors are parallel if one is a scalar multiple of the other, meaning their components are proportional. For example, if v = k * w for some scalar k, then v and w point in the same or opposite direction, indicating parallelism.
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Orthogonal Vectors and the Dot Product
Vectors are orthogonal (perpendicular) if their dot product equals zero. The dot product is calculated by multiplying corresponding components and summing the results. If v · w = 0, the vectors form a right angle.
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