Did I Make a Mistake in my Matrix Multiplication?

  • Thread starter Thread starter r-soy
  • Start date Start date
AI Thread Summary
The discussion centers on a user's concern about potential mistakes in their matrix multiplication answers from a timed exam. They specifically note an error in the upper right number of the first question's answer, while the other answers appear correct. Additionally, it is mentioned that the second multiplication involved an identity matrix, which did not require a detailed write-out. The conversation emphasizes the importance of accuracy in matrix multiplication and the distinction of the identity matrix. Overall, the user seeks validation of their answers and clarification on the identity matrix's handling.
r-soy
Messages
170
Reaction score
1
Hi all

I want check my answers​
 

Attachments

  • QQQQQ.JPG
    QQQQQ.JPG
    15.1 KB · Views: 371
  • 11111111111.JPG
    11111111111.JPG
    29.7 KB · Views: 410
  • 22222222222.JPG
    22222222222.JPG
    37.8 KB · Views: 437
Physics news on Phys.org
r-soy said:
Hi all

I want check my answers​

It says it was a timed exam?
 
The upper right number in the answer of the first question is wrong. The rest is Ok.

The second matrix multiplication was with an unity matrix. You didn't have to write that one out.
 
willem2 said:
The upper right number in the answer of the first question is wrong. The rest is Ok.

The second matrix multiplication was with an unity matrix. You didn't have to write that one out.
Usually called identity matrix.
 

Thread 'Family of lines that are at a distance of 5 from the origin'

I picked up this problem from the Schaum's series book titled "College Mathematics" by Ayres/Schmidt. It is a solved problem in the book. But what surprised me was that the solution to this problem was given in one line without any explanation. I could, therefore, not understand how the given one-line solution was reached. The one-line solution in the book says: The equation is ##x \cos{\omega} +y \sin{\omega} - 5 = 0##, ##\omega## being the parameter. From my side, the only thing I could...
View full post »

Thread 'Making the denominator of a certain fraction real'

Essentially I just have this problem that I'm stuck on, on a sheet about complex numbers: Show that, for ##|r|<1,## $$1+r\cos(x)+r^2\cos(2x)+r^3\cos(3x)...=\frac{1-r\cos(x)}{1-2r\cos(x)+r^2}$$ My first thought was to express it as a geometric series, where the real part of the sum of the series would be the series you see above: $$1+re^{ix}+r^2e^{2ix}+r^3e^{3ix}...$$ The sum of this series is just: $$\frac{(re^{ix})^n-1}{re^{ix} - 1}$$ I'm having some trouble trying to figure out what to...
View full post »

Similar threads

Where is the mistake in my probability calculation for a 20cm string cut?
Replies
2
Views
1K
Transformations to both sides of a matrix equation
Replies
25
Views
2K
Finding a Mistake: Probability of Y with X and Spins
Replies
7
Views
2K
Matrix Function - Check Understanding
Replies
7
Views
1K
Example Required: Matrix Solution By Dividing into Quadrants
Replies
8
Views
2K
Matrix Multiplication Homework: Equations and Solutions"
Replies
3
Views
2K
Did my textbook make a mistake when writing these units?
Replies
5
Views
755
Prove that if n^2 is a multiple of 2, then n is multiple of 2
Replies
23
Views
4K
Matrices: if AB=A and BA=B, then B^2 is equal to?
Replies
18
Views
3K
Find the rank of this 3x3 matrix
Replies
6
Views
2K

Hot Threads

Recent Insights

Back
Top