Chapter 12: Problem 13
Find the component form of the vector. The unit vector that makes an angle \(\theta=2 \pi / 3\) with the positive \(x\) -axis
Short Answer
Expert verified
The component form of the vector is \( \left(-\frac{1}{2}, \frac{\sqrt{3}}{2}\right) \).
Step by step solution
01
Understanding the Unit Circle
To find the component form of the vector, we start by understanding what a unit vector is. A unit vector has a magnitude of 1. The angle given is \( \theta = \frac{2\pi}{3} \), which is in radians. It corresponds to 120 degrees on the unit circle.
02
Find the Components Using Trigonometry
On the unit circle, a vector making an angle \( \theta \) with the positive x-axis can be represented as \( (\cos(\theta), \sin(\theta)) \). Here, \( \theta = \frac{2\pi}{3} \). Therefore, the x-component of the vector is \( \cos\left(\frac{2\pi}{3}\right) \) and the y-component is \( \sin\left(\frac{2\pi}{3}\right) \).
03
Calculate the Components
Calculate the cosine component: \( \cos\left(\frac{2\pi}{3}\right) = -\frac{1}{2} \). Calculate the sine component: \( \sin\left(\frac{2\pi}{3}\right) = \frac{\sqrt{3}}{2} \).
04
Write the Component Form
The vector in component form is \( \left(-\frac{1}{2}, \frac{\sqrt{3}}{2}\right) \). This keeps the magnitude of the vector as 1, confirming it's a unit vector.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Unit Circle
The unit circle is a fundamental concept in trigonometry and vector analysis. Imagine a circle with a radius of 1, centered at the origin of a coordinate system. That's the unit circle. It helps us visualize and calculate trigonometric functions: cosine and sine.
Let's break it down further:
Let's break it down further:
- For any angle \( \theta \) measured counterclockwise from the positive x-axis, the coordinates on the unit circle are \((\cos(\theta), \sin(\theta))\).
- These coordinates correspond to the x and y components of a vector on the unit circle.
- An angle \( \theta = \frac{2\pi}{3} \) radians corresponds to 120 degrees.
Trigonometry
When exploring vectors and unit circles, trigonometry plays a crucial role. It connects angles and ratios of triangle sides, which helps in determining positions on the unit circle.
In the context of vectors:
In the context of vectors:
- Cosine \( \cos(\theta) \) gives the x-coordinate of a point on the unit circle for an angle \( \theta \).
- Sine \( \sin(\theta) \) gives the y-coordinate.
- For \( \theta = \frac{2\pi}{3} \):
- \( \cos\left(\frac{2\pi}{3}\right) = -\frac{1}{2} \) is the x-component.
- \( \sin\left(\frac{2\pi}{3}\right) = \frac{\sqrt{3}}{2} \) is the y-component.
Component Form
The component form of a vector expresses it as an ordered pair, indicating how far it travels in the x and y directions. For example, \((x, y)\) for a vector represents:
- The x-component as how far it moves horizontally.
- The y-component as how far it moves vertically.
- The x-component \( = -\frac{1}{2} \)
- The y-component \( = \frac{\sqrt{3}}{2} \)
Unit Vector
In vector mathematics, a unit vector is crucial because it has a magnitude of 1 and provides direction. It lies on the unit circle due to its consistent magnitude.
Here's why unit vectors matter:
Remember, whenever you're working with vectors on the unit circle, you're essentially dealing with unit vectors, making them pivotal in understanding directions and components.
Here's why unit vectors matter:
- They serve as building blocks for defining directions in space.
- In applications like physics, they simplify calculations by providing direction without changing a vector's strength.
Remember, whenever you're working with vectors on the unit circle, you're essentially dealing with unit vectors, making them pivotal in understanding directions and components.