Chapter 1: Problem 59
Find the component form of vector \(\mathbf{u}\), given its magnitude and the angle the vector makes with the positive \(x\) -axis. Give exact answers when possible. $$ \|\mathbf{u}\|=10, \theta=\frac{5 \pi}{6} $$
Short Answer
Expert verified
The component form of vector \( \mathbf{u} \) is \( (-5\sqrt{3}, 5) \).
Step by step solution
01
Understand Vector Representation
To find the component form of the vector \( \mathbf{u} \), we need to know its magnitude \( \|\mathbf{u}\| \) and the angle \( \theta \) it makes with the positive x-axis. The component form is generally given by \((x, y)\), where \(x\) and \(y\) are the horizontal and vertical components, respectively.
02
Calculate the Horizontal Component
The horizontal component \( x \) of vector \( \mathbf{u} \) is given by \( x = \|\mathbf{u}\| \cdot \cos(\theta) \). Substituting the given values, we have:\[ x = 10 \cdot \cos\left(\frac{5\pi}{6}\right) \]Using the value \( \cos\left(\frac{5\pi}{6}\right) = -\frac{\sqrt{3}}{2} \), we find:\[ x = 10 \cdot \left(-\frac{\sqrt{3}}{2}\right) = -5\sqrt{3} \]
03
Calculate the Vertical Component
The vertical component \( y \) of vector \( \mathbf{u} \) is given by \( y = \|\mathbf{u}\| \cdot \sin(\theta) \). Substituting the given values, we have:\[ y = 10 \cdot \sin\left(\frac{5\pi}{6}\right) \]Using the value \( \sin\left(\frac{5\pi}{6}\right) = \frac{1}{2} \), we find:\[ y = 10 \cdot \frac{1}{2} = 5 \]
04
Write the Component Form
Combining the calculated components from Steps 2 and 3, the component form of vector \( \mathbf{u} \) is given by \( (x, y) = (-5\sqrt{3}, 5) \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Magnitude of a Vector
The magnitude of a vector, often denoted as \( \|\mathbf{u}\| \), essentially represents the length or size of the vector. Think of it as a measure of how far the vector extends in space. In our example, the magnitude is given as 10. This means the vector stretches out to a length of 10 units.
To calculate the magnitude of a vector from its components, you can use the formula \( \sqrt{x^2 + y^2} \), where \( x \) and \( y \) are the horizontal and vertical components respectively. Here's the step-by-step thought process:
To calculate the magnitude of a vector from its components, you can use the formula \( \sqrt{x^2 + y^2} \), where \( x \) and \( y \) are the horizontal and vertical components respectively. Here's the step-by-step thought process:
- Imagine a vector drawn from the origin in a coordinate system.
- The magnitude is essentially the "hypotenuse" of a right triangle formed by drawing horizontal and vertical components from the vector's endpoint to the respective axes.
- This vector's magnitude can also equal the sum of the squares of its components, thanks to the Pythagorean theorem.
Angle with x-axis
The angle a vector makes with the x-axis, often denoted as \( \theta \), plays a vital role in determining the direction of the vector.
- In our exercise, this angle is \( \theta = \frac{5\pi}{6} \).
- This value implies that the vector is located in the second quadrant of the unit circle because \( \frac{5\pi}{6} \) is between \( \frac{\pi}{2} \) and \( \pi \).
- A full circle is \( 2\pi \) radians, so \( \frac{5\pi}{6} \) is more than half of \( \pi \), making it a broad stretch around to the left of the x-axis.
- This specific angle directly influences the horizontal and vertical components of the vector, impacting how it is projected along each axis.
Trigonometric Components
To break a vector down into its components, we use basic trigonometry, which involves sine and cosine functions. These functions help us determine the horizontal (x) and vertical (y) components of a vector:
- Horizontal Component: The horizontal component \( x \) is found using \( x = \|\mathbf{u}\| \cdot \cos(\theta) \). For our exercise, substituting the values, we have \( x = 10 \cdot \cos\left(\frac{5\pi}{6}\right) = -5\sqrt{3} \).
- Vertical Component: The vertical component \( y \) is determined by \( y = \|\mathbf{u}\| \cdot \sin(\theta) \), leading to \( y = 10 \cdot \sin\left(\frac{5\pi}{6}\right) = 5 \).
- Cosine links to the horizontal span: how far over the x-axis the vector is.
- Sine ties to the vertical reach: how far up it goes.