In Exercises 47–52, write the vector v in terms of i and j whose magnitude ||v|| and direction angle θ are given. ||v|| = 6, θ = 30°
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8. Vectors
Geometric Vectors
Problem 63
Textbook Question
In Exercises 61–64, find the magnitude ||v||, to the nearest hundredth, and the direction angle θ, to the nearest tenth of a degree, for each given vector v. v = (4i - 2j) - (4i - 8j)
Verified step by step guidance1
First, simplify the given vector expression by subtracting the components of the vectors: \(\mathbf{v} = (4\mathbf{i} - 2\mathbf{j}) - (4\mathbf{i} - 8\mathbf{j})\). This means subtract the \(i\) components and the \(j\) components separately.
Calculate the \(i\) component of \(\mathbf{v}\) by subtracting: \$4 - 4 = 0\(. Calculate the \)j\( component of \(\mathbf{v}\) by subtracting: \)-2 - (-8) = -2 + 8 = 6$. So, \(\mathbf{v} = 0\mathbf{i} + 6\mathbf{j}\).
Find the magnitude \(||\mathbf{v}||\) using the formula for the magnitude of a vector: \(||\mathbf{v}|| = \sqrt{(v_x)^2 + (v_y)^2}\), where \(v_x\) and \(v_y\) are the components of \(\mathbf{v}\).
Substitute the components into the magnitude formula: \(||\mathbf{v}|| = \sqrt{0^2 + 6^2} = \sqrt{36}\). This will give the length of the vector.
To find the direction angle \(\theta\), use the formula \(\theta = \tan^{-1}\left(\frac{v_y}{v_x}\right)\). Since \(v_x = 0\), consider the position of the vector on the coordinate plane to determine \(\theta\) correctly.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Vector Subtraction
Vector subtraction involves subtracting corresponding components of two vectors. For vectors in component form, subtract the i-components and j-components separately to find the resultant vector. This operation is essential to determine the vector v given by (4i - 2j) - (4i - 8j).
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Magnitude of a Vector
The magnitude (or length) of a vector v = ai + bj is found using the Pythagorean theorem: ||v|| = √(a² + b²). This scalar value represents the distance from the origin to the point (a, b) in the plane and is crucial for quantifying the size of the vector.
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Direction Angle of a Vector
The direction angle θ of a vector is the angle it makes with the positive x-axis, measured counterclockwise. It can be found using θ = arctan(b/a), where a and b are the vector's components. Adjustments may be needed based on the quadrant to get the correct angle.
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