/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 152 It's not hard to see that in the... [FREE SOLUTION] | 91Ó°ÊÓ

91Ó°ÊÓ

It's not hard to see that in the plane, the largest number of nonzero vectors that can be chosen so that any two of the vectors make the same nonzero angle with each other is 3 (and the only possible nonzero angle for three such vectors to make is \(2 \pi / 3)\). Now suppose we have vectors in \(n\) dimensional space. What is the largest possible number of nonzero vectors in \(n\)-space so that the angle between any two of the vectors is the same (and not zero)? In that situation, what are the possible values for the angle?

Short Answer

Expert verified
The maximum number of vectors is \(n+1\) and the angle between any two vectors is \(\arccos\left(-\frac{1}{n}\right)\).

Step by step solution

01

Define the problem in n-dimensional space

We need to find the largest number of nonzero vectors in \(n\)-dimensional space such that the angle between any pair of vectors is the same and not zero.
02

Understand the 2-dimensional case

In 2-dimensional space, it's known that the largest number of nonzero vectors making the same nonzero angle with each other is 3. The possible angle for three such vectors is \(\frac{2\pi}{3} = 120^\text{o}\). This is because the vectors form an equilateral triangle when represented.
03

Generalize to n-dimensional space

Consider \(n\)-dimensional space. Any set of nonzero vectors that make the same angle with each other must form a regular simplex. In \(n\)-dimensional space, a regular simplex has \(n+1\) vertices.
04

Apply the condition for equal angles

The largest number of vectors that can all make the same nonzero angle with each other in \(n\)-dimensional space is \(n+1\).
05

Determine the angle

Let’s find the angle between these vectors. For a regular simplex, the angle \(\theta\) between any two vectors can be calculated using the formula for the cosine of the angle between vectors forming a regular simplex. The cosine of the angle between any two vectors in an \(n\)-dimensional regular simplex is given by \(\cos(\theta) = -\frac{1}{n}\). Consequently, the angle \(\theta\) is \(\arccos\left(-\frac{1}{n}\right)\).

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!

Key Concepts

These are the key concepts you need to understand to accurately answer the question.

vector angles
When working with vectors in any dimensional space, the angle between them is crucial. This angle helps us understand how vectors are oriented with respect to each other. To find the angle between two vectors, we often use the cosine formula. This formula relates the angle to the dot product of the vectors and their magnitudes. Here's the formula:

The cosine of the angle \(\theta\) between two vectors \(\textbf{u}\) and \(\textbf{v}\) is:
\[\cos(\theta) = \frac{\textbf{u} \bullet \textbf{v}}{\text{\|}\textbf{u}\text{\|} \text{\|}\textbf{v}\text{\|}}\]

Let's break this down:

- \(\textbf{u} \bullet \textbf{v}\) is the dot product of \(\textbf{u}\) and \(\textbf{v}\)
\t
  • The dot product is calculated as the sum of the products of their corresponding components.
  • \(\text{\|}\textbf{u}\text{\|}\) and \(\text{\|}\textbf{v}\text{\|}\) are the magnitudes (or lengths) of \(\textbf{u}\) and \(\textbf{v}\), respectively.
Understanding vector angles helps us grasp the concept of vectors pointing in various directions in space. This will be especially important in higher dimensions where we deal with more complex shapes.

regular simplex
A regular simplex is a geometric shape that generalizes the concept of a triangle and a tetrahedron to any dimension. In 2D space, a regular simplex is an equilateral triangle, and in 3D space, it's a tetrahedron. For an \(n\)-dimensional space, a regular simplex is formed by \(n+1\) vectors.

What makes a regular simplex unique?
  • All of its elements (vertices, edges, etc.) are equally distant from each other.

In the context of vectors, a regular simplex has the property that any two vectors form the same angle with each other. This arrangement is incredibly symmetrical and uniform. Understanding regular simplices in higher dimensions can help us deepen our appreciation for the beauty and symmetry in geometry.

cosine formula
The cosine formula is essential for finding angles between vectors. When we work with \(n\)-dimensional regular simplices, it allows us to determine the exact angle formed between any two vectors.
  • For a regular simplex in \(n\)-dimensional space, the cosine of the angle \(\theta\) between any two vectors is \(\cos(\theta) = -\frac{1}{n}\).
Here's how this formula helps us:
  • It gives us a concrete way to calculate angles in higher-dimensional geometry.
  • It generalizes our understanding of angles from simple triangles to complex shapes in many dimensions.
Using this formula, we can further explore the geometric properties of vectors and shapes in \(n\)-dimensional space. For instance, we can compute the exact angle as:
\[\theta = \arccos\left(-\frac{1}{n}\right)\]
Math in higher dimensions can be challenging, but with formulas like this, we gain powerful tools to unravel complex concepts.

n-dimensional geometry
In n-dimensional geometry, we step beyond the familiar realms of 2D and 3D. Here, we deal with spaces that have more than three dimensions. These spaces are abstract, but they are essential for various fields like physics, mathematics, and computer science.

Key aspects of n-dimensional geometry include:
  • Generalizations of shapes like triangles and tetrahedrons to higher dimensions (think of regular simplices).
  • Understanding angles, distances, and other geometric properties in spaces with more than three dimensions.
Geometry in n-dimensions helps us model complex systems and solve problems that are hard to visualize in 2D or 3D. While it may seem complicated, breaking down concepts like vector angles and regular simplices simplifies our understanding and allows us to see the elegance in higher-dimensional spaces.

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

a. Find all lines which are tangent to both of the parabolas $$ y=x^2 \quad \text { and } \quad y=-x^2+4 x-4 $$ b. Now suppose \(f(x)\) and \(g(x)\) are any two quadratic polynomials. Find geometric criteria that determine the number of lines tangent to both of the parabolas \(y=f(x)\) and \(y=g(x)\).

Suppose we start with a Pythagorean triple \((a, b, c)\) of positive integers, that is, positive integers \(a, b, c\) such that \(a^2+b^2=c^2\) and which can therefore be used as the side lengths of a right triangle. Show that it is not possible to have another Pythagorean triple \((b, c, d)\) with the same integers \(b\) and \(c\); that is, show that \(b^2+c^2\) can never be the square of an integer.

Let \(S\) be a set of numbers which includes the elements 0 and 1 . Suppose \(S\) has the property that for any nonempty finite subset \(T\) of \(S\), the average of all the numbers in \(T\) is an element of \(S\). Prove or disprove: \(S\) must contain all the rational numbers between 0 and 1 .

Suppose we are given an \(m\)-gon (polygon with \(m\) sides, and including the interior for our purposes) and an \(n\)-gon in the plane. Consider their intersection; assume this intersection is itself a polygon (other possibilities would include the intersection being empty or consisting of a line segment). a. If the \(m\)-gon and the \(n\)-gon are convex, what is the maximal number of sides their intersection can have? b. Is the result from (a) still correct if only one of the polygons is assumed to be convex? (Note: A subset of the plane is convex if for every two points of the subset, every point of the line segment between them is also in the subset. In particular, a polygon is convex if each of its interior angles is less than \(\left.180^{\circ}.\right)\)

Let \(f_1, f_2, \ldots, f_{2012}\) be functions such that the derivative of each of them is the sum of the others. Let \(F=f_1 f_2 \cdots f_{2012}\) be the product of all these functions. Find all possible values of \(r\), given that \(\lim _{x \rightarrow-\infty} F(x) e^{r x}\) is a finite nonzero number.

See all solutions

Recommended explanations on Math Textbooks

View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.