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Ch. 7 - Applications of Trigonometry and Vectors
Lial - Trigonometry 12th Edition
Lial12th EditionTrigonometryISBN: 9780136552161Not the one you use?Change textbook
Chapter 8, Problem 41c

Given vectors u and v, find: v - 3u. 
u = 2i, v = i + j

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1
Identify the given vectors: \( \mathbf{u} = 2\mathbf{i} \) and \( \mathbf{v} = \mathbf{i} + \mathbf{j} \).
Multiply vector \( \mathbf{u} \) by the scalar 3: calculate \( 3\mathbf{u} = 3 \times 2\mathbf{i} \).
Express \( 3\mathbf{u} \) in component form after multiplication.
Subtract \( 3\mathbf{u} \) from \( \mathbf{v} \) by subtracting corresponding components: \( \mathbf{v} - 3\mathbf{u} = (\mathbf{i} + \mathbf{j}) - (\text{components of } 3\mathbf{u}) \).
Write the resulting vector in terms of \( \mathbf{i} \) and \( \mathbf{j} \) components to complete the expression for \( \mathbf{v} - 3\mathbf{u} \).

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Key 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 as sums of their components along the coordinate axes, typically using unit vectors i and j for the x and y directions. For example, u = 2i means the vector has a magnitude of 2 along the x-axis and zero along the y-axis.
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Scalar Multiplication of Vectors

Scalar multiplication involves multiplying each component of a vector by a scalar value. For instance, multiplying vector u by 3 scales its magnitude by 3, resulting in 3u = 6i if u = 2i.
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Multiplying Vectors By Scalars

Vector Addition and Subtraction

Adding or subtracting vectors is done component-wise by combining their respective i and j components. To find v - 3u, subtract the components of 3u from those of v, resulting in a new vector.
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Adding Vectors Geometrically