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Ch. 4 - Laws of Sines and Cosines; Vectors
Blitzer - Trigonometry 3rd Edition
Blitzer3rd EditionTrigonometryISBN: 9780137316601Non è quello che usi tu?Cambia libro di testo
Capitolo 4, Problema 63

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)

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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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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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Finding Magnitude of a Vector

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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Finding Direction of a Vector