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Linear Algebra

Linear algebra is the detailed study of vector spaces. With applications in such disparate fields as sociology, economics, computer programming, chemistry, and physics, including its essential role in mathematically describing quantum mechanics and the theory of relativity, linear algebra has become one of the most essential mathematical disciplines for the modern world. Please direct all questions regarding matrices, determinants, eigenvalues, eigenvectors, and linear transformations into this category.

2,176 Questions

Who is the commutative property in dot and cross product?

The cross product results in a vector quantity that follows a right hand set of vectors; commuting the first two vectors results in a vector that is the negative of the uncommuted result, ie A x B = - B x A

The dot product results in a scalar quantity; its calculation involves scalar (ie normal) multiplication and is unaffected by commutation of the vectors, ie A . B = B . A

How do you write 35.5 billion in standard form?

The word "billion" as used in English-speaking countries means 109 (a one, followed by 9 zeros). Therefore, to convert this to standard form, you simply move the decimal point 9 positions to the right - filling out with zeros as needed.

What is -10408x?

It is a negative multiple of x.

It is a negative multiple of x.

It is a negative multiple of x.

It is a negative multiple of x.

Different types of input and output tables?

Input and output tables are used to organize data for various purposes. Common types include truth tables in logic that display the relationship between inputs and outputs for logical expressions, and function tables that show how different input values produce specific outputs in mathematical functions. Additionally, data tables in databases organize records with defined fields for efficient data retrieval and analysis. These tables help visualize relationships and facilitate decision-making across various fields.

Why do cross products work?

There was a time when this rule was considered a wonderful piece of magic, called the "rule of three"; students just learned to do it without expecting to understand why it worked. That makes me sad! With algebra, it's almost obvious, and certainly not something special. I'll try to express this in a way that students who don't know algebra (or don't realize how much of it they have already seen) can follow. Remember that if you have two equal quantities and multiply them by the same amount, the products will again be equal. So if we multiply the fractions a/b and c/d by b, the results are equal: a c --- * b = --- * b b d which can be written as bc a = ---- d Now we can multiply both fractions by d: bc ad = ---- * d d which, of course, means ad = bc I personally prefer not to cross multiply, but just to multiply by whichever denominator helps. In your example, 3/15 = n/30, I would just multiply both sides by 30 and get n = 30*3/15 = 30/15*3 = 2*3 = 6.

I would like to add that cross products are used to find the unknown of a proportion (or ratio) that already exists by the nature of the equality.

For example a recipe calls for 2 cups of flour to make 4 pancakes but I want 12.

I can say 2 is to 4 what x is to 12 and set up the ratio:

2/4 :: x/12

2 x 12 = 4x (cross multiply)

24 = 4x

24/4 = x (and divide)

x = 6 cups of flour

this method is also used (transparently) in chemistry and engineering, and is crucial in solving algebraic equations.

Is the Speed Sensor and the Speedo Head the same thing for a 95 Ford Taurus?

No. The speed sensor is located on the transmission, and is what drives the speedometer cable, which drives the speedo head. The speedo head is another name for the the speedometer, which is the display gauge that you see while sitting in the car.

What two numbers multiplies out to -600 and adds up to ten?

In the case I would first write ALL factors of 600 and find the differences.

1x600

2x300

3x200

4x150

5x120

6x100

8x75

10x60

12x50

15x40

20x30

24x25

The one that subtracts to give the answer is -20 and 30

C program to check whether a given matrix is orthogonal or not?

#include<iostream>

#include<stdio.h>

#include<conio.h>

using namespace std;

int main()

{

int a[20][20],b[20][20],c[20][20],i,j,k,m,n,f;

cout << "Input row and column of A matrix \n\n";

cin >> n >> m;

cout << "\n\nInput A - matrix \n\n";

for(i=0;i<n;++i)

for(j=0;j<m;++j)

cin >> a[i][j];

cout << "\n\nMatrix A : \n\n";

for(i=0;i<n;++i)

{

for(j=0;j<m;++j)

cout << a[i][j] << " ";

cout << "\n\n";

}

for(i=0;i<m;++i)

for(j=0;j<n;++j)

b[i][j]=a[j][i];

cout << "\n\nTranspose of matrix A is : \n\n";

for(i=0;i<m;++i)

{

for(j=0;j<n;++j)

cout << b[i][j] << " ";

cout << "\n\n";

}

for(i=0;i<m;i++)

{

for(j=0;j<m;j++){

c[i][j]=0;

for(k=0;k<=m;k++)

c[i][j]+=a[i][k]*b[k][j];

}

}

for(i=0;i<m;i++)

{

for(j=0;j<m;j++)

{

if((int)c[i][i]==1&&(int)c[i][j]==0)

f=1;

}

}

cout<<"\n\n Matrix A * transpose of A \n\n";

for(i=0;i<m;i++)

{

for(j=0;j<m;j++)

cout << c[i][j];

cout << "\n\n";

}

if(f==1)

cout << "\n\nMatrix A is Orthogonal !!!";

else

cout << "\n\nMatrix A is NOT Orthogonal !!!";

getch();

return 0;

}

-ALOK

How can I prove that similar matrices have same eigenvalues?

First, we'll start with the definition of an eigenvalue. Let v be a non-zero vector and A be a linear transformation acting on v. k is an eigenvalue of the linear transformation A if the following equation is satisfied:

Av = kv

Meaning the linear transformation has just scaled the vector, v, not changed its direction, by the value, k.

By definition, two matrices, A and B, are similar if B = TAT-1, where T is the change of basis matrix.

Let w be some vector that has had its base changed via Tv.

Therefore v = T-1w

We want to show that Bw = kv

Bw = TAT-1w = TAv = Tkv = kTv= kw

Q.E.D.

What are some real life examples of vertical line slope?

  • corners of most buildings
  • sides of picture frames
  • sides of rectangular windows
  • corners of kitchen refrigerators and stoves

What are three equations for y equals -2x?

All that matters once you have y = -2x is the y-intercept.

Examples:

y = -2x +3

y = -2x - 8

y = -2x + 4

You can change the y-intercept to whatever numbers you want.

One extra hint: All the lines with the slope of -2x will be parallel on a graph, no matter what the y-intercept is.

When would you use a system of equations?

When you are dealing with a number of variables and relations between them.

What is 6x plus 3y-2x plus 5y?

6x plus 3y minus 2x plus 5y equals 4x plus 8y.

Do you solve an expression the same way you solve an equation?

If we are talking about the algebraic expressions, then an expression can be simplified or be evaluated for specific values of its variables, while an equation need to be solved, in other words to find the values of the variables that make the equation a true statement.

If we are solving an equation, then we can work in the same way that we can simplify an expression (since an equation is a statement that states that two expressions are equal), or factoring an expression.

What are the solutions to the equation 25x2-1000?

Since it has no equal sign, this isn't an equation. I believe you have to spell it out as "equals" in your question, due to restrictions imposed by Answers.com.

What is meant by tridiagonal matrix?

A tridiagonal matrix is one in which the only non-zero elements are on the principal diagonal, and the two diagonals immediately next to it: one below and the other above.