If vectors and , and , determine the angle between vectors and .
Table of contents
- 0. Review of College Algebra4h 45m
- 1. Measuring Angles40m
- 2. Trigonometric Functions on Right Triangles2h 5m
- 3. Unit Circle1h 19m
- 4. Graphing Trigonometric Functions1h 19m
- 5. Inverse Trigonometric Functions and Basic Trigonometric Equations1h 41m
- 6. Trigonometric Identities and More Equations2h 34m
- 7. Non-Right Triangles1h 38m
- 8. Vectors2h 25m
- 9. Polar Equations2h 5m
- 10. Parametric Equations1h 6m
- 11. Graphing Complex Numbers1h 7m
8. Vectors
Dot Product
Problem 3
Textbook Question
In Exercises 1–8, use the given vectors to find v⋅w and v⋅v. v = 5i - 4j, w = -2i - j
Verified step by step guidance1
Identify the components of the vectors \( \mathbf{v} = 5\mathbf{i} - 4\mathbf{j} \) and \( \mathbf{w} = -2\mathbf{i} - \mathbf{j} \). Here, \( \mathbf{v} = (5, -4) \) and \( \mathbf{w} = (-2, -1) \).
Recall the formula for the dot product of two vectors \( \mathbf{a} = (a_1, a_2) \) and \( \mathbf{b} = (b_1, b_2) \):
\[
\mathbf{a} \cdot \mathbf{b} = a_1 b_1 + a_2 b_2
\]
Calculate \( \mathbf{v} \cdot \mathbf{w} \) by multiplying corresponding components and adding the results:
\[
\mathbf{v} \cdot \mathbf{w} = (5)(-2) + (-4)(-1)
\]
Recall that \( \mathbf{v} \cdot \mathbf{v} \) is the dot product of \( \mathbf{v} \) with itself, which gives the square of its magnitude:
\[
\mathbf{v} \cdot \mathbf{v} = 5^2 + (-4)^2
\]
Perform the arithmetic operations in the expressions from steps 3 and 4 to find the values of \( \mathbf{v} \cdot \mathbf{w} \) and \( \mathbf{v} \cdot \mathbf{v} \).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Dot Product of Vectors
The dot product is an algebraic operation that takes two vectors and returns a scalar. It is calculated by multiplying corresponding components of the vectors and summing the results. For vectors v = ai + bj and w = ci + dj, the dot product is v·w = ac + bd.
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Introduction to Dot Product
Vector Components
Vectors in two dimensions can be expressed in terms of their components along the i (x-axis) and j (y-axis) unit vectors. Understanding how to identify and use these components is essential for operations like addition, subtraction, and dot product.
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Position Vectors & Component Form
Dot Product of a Vector with Itself
The dot product of a vector with itself, v·v, gives the square of its magnitude. It is calculated by summing the squares of its components, i.e., v·v = a² + b² for v = ai + bj. This is useful for finding the length or magnitude of the vector.
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Introduction to Dot Product
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