Math / Science

The Math / Science topic primarily includes discussions of mathematics, physics, statistics and economic analysis, but also biology, chemistry and other sciences.

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STEM education is growing rapidly and preparing the next generation to fulfill the needs of our society's technology demands.  

In what ways has EE helped you continually learn, even as professionals?
How can EE support STEM as a great learning resource?
HTML5 and CSS3 Fundamentals
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HTML5 and CSS3 Fundamentals

Build a website from the ground up by first learning the fundamentals of HTML5 and CSS3, the two popular programming languages used to present content online. HTML deals with fonts, colors, graphics, and hyperlinks, while CSS describes how HTML elements are to be displayed.

I have an image which is 320x240 px

I have an array of values for each pixel in the image (76,800 points)

If the user hovers over any part of the image I need to look at the array and return the corresponding value for it.

X Y position [0,0] of the image = the first value in the array.

If I wanted to find out the X Y position [65,33] of the image, and then look up the  value in the array, what would be the correct forumla to do this
Well I was revising how 'magnetic' force is created and I came up to an issue?

Why do we measure only the charge net density only from a frame reference that electrons dont move?
I recently drove my car into the outside of my house and the circa 1860 plaster fell off the inside wall due to the impact.

The house is still structurally sound but the plaster that fell off the inside wall really smells bad. What is creating that horrible smell and how can I get rid of it?
We have a reference system in a conducting coil . Our reference velocity is the velocity of current(electrons).

Why the spacing between the nuclei is smaller than if we take as reference system with reference velocity the velocity of nuclei?

Length contraction decreases the dimensions of the nuclei , not making smaller the spacing between the nuclei.
Are LED's forward voltage dependent on the type of the semiconductor?

For example if a Led emmits red light is its forward different from a LED that emmits blue light?
Hello and Good Morning Everyone,

           I am wondering why C14 (subscript) would be used in a disinfectant/virucide.  I always thought that it a radioactive substance used in carbon dating of very old materials by archeologists and nothing else.   If used in a day to day disinfectant/virucide, could it be considered potentially carcinogenic to humans?

           Any feedback given to this question will be appreciated.

           Thank you

Why when I increase the  base resistor  the VCE voltage drop dicreases?
Hello and Good Evening Everyone,

        From a label on a disinfectant viricide bottle, I noticed an area listed as Inert Ingredients with a percentage of 99.93%.  Didecyl dimethyl ammonium chloride being  .04% and dimethyl benzyl ammonium chloride being  .03%.  Given this information, I am wondering what is meant by Inert Ingredients.  

         Any clarification which can be given for the meaning of Inert Ingredients will be greatly appreciated.  

         Thank you

Attached is Matlab command to convert polar form to rectangular form.  I'm converting 2e^j(pi/2) to rectangular form.

I was expecting real part to be 0 but it's a very small number.  Is this because there isn't enough bits to represent 0?
Introduction to Web Design
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Introduction to Web Design

Develop a strong foundation and understanding of web design by learning HTML, CSS, and additional tools to help you develop your own website.

Nonstop train leaves Toronto and Montreal at the same time each day going to the other city along the main line. One trai travels at 120km/h and the other at 90km/h. Assuming the train is straight, how apart are they one hour before they meet?

The distance between Toronto ans Sudbury is 418 km. Terry leaves Sudbury on his motorcycle and went 105 km towards Toronto. Damon left Toronto at the same time on his motorcycle and drove 215 km towards Sudbury. How apart are Terry and Damon ?

Be a power thinker and solve this number puzzle by finding the correct values for A and B. The pictures are important

      A - B = 2                                  A(A in square) + 2 = B(B in cube)
For a number sequence A: (1, 2, 3, 4, 5, 6, 7, 8, 9, 10)

Are the terms in the subset B: (1, 4, 7, 8) considered in sequence given that some numbers from A were skipped?

Should I use the adjective sequential or succedent, or is there a better word?
Micheal has 16.25 $ in the bank. He needs 108 $ to buy a video game. He finds he can save 1.75 $ a week from his allowance. How many weeks must he save in order to have enough to buy the game.
Jenny has pennies , nickels , dimes , quarters , half dollars and/or dollar in her purse. still shes unable to make change for aa old two dollar bill.what is the greatsest amount of money she could possibly have.(She may have none of some of the coins.)

Barb has five small chains of three links each. She wants to make them into one long chain of 15 links. If cutting a link costs 20 cents and wedling a link costs 1.50$ what is the least cost of making the chain (Hint: You can do it for less than 6.80$.

Stefan is working on his garden. All of the flowers in the garden were white expect two,all are red except two and all are yellow except two. How many flowers are in stefan's garden.

in how many ways can change be made for for 85 cents using nothing but but nickels and/or dimes

I never tire of asking me: To be a good programmer, what is the relevance of getting a degree in computer science? And a good programmer has in mind all the commands of a programming language, like PHP or JAVA? The oldest languages (MSDOS) had less than 200 commands and functions, currently they must have more than 1000

I would like to hearing from you

Consider a binomial random variable X ~ Bi(n,∅).

We can get P(x) and P(x+1) as below but how to solve question 1 & 2 ?

P(x) = nCx . ∅ x (1- ∅)n-x
p(x+1) = nC x+1 . ∅ x-1 (1- ∅) n- (x+1)
Dear experts,

I was looking at videos which complement Good notes 4. I can came across the one below:

The presenter is discussing, at time scale 8m  32sec, an app where i could write math formulae (not using key board) on an app and it calculated the result.
I have my Itunes account with country as India. I do not think it is available for India Itunes account.

I use good notes for writing my MAth theorems from Real analysis, measure and integration, number theory, linear algebra, vector spaces, ODE/PDE, probability.

Kindly can anyone provide me a list of similar apps ranked by preference.

I will then look for those which are available for India.


Thank you
What is the date today if april 29 was nine days before two days after three days preceding the day before five days following the day before yesterday?

Ray and a friend drive from vancouver to toronto in 56 h of steady driving, They leave vancouver on may 30 8 am when do they arrive in toronto
I'm wondering if the following makes sense to define the sequence of points that make up the shapes? Not sure of the proper way to describe the sequence so any help to improve the formula will be appreciated. A289006 relates to the number sequence at Thanks.

shape sequence Fibonacci numbers x A289006
Exploring ASP.NET Core: Fundamentals
LVL 12
Exploring ASP.NET Core: Fundamentals

Learn to build web apps and services, IoT apps, and mobile backends by covering the fundamentals of ASP.NET Core and  exploring the core foundations for app libraries.

I've having trouble with a rounding routine in Excel.  The goal is when the user enters a number with the wrong number of significant digits, the macro rounds the number and replaces what they entered.  It does not merely change the cell display to show the desired number of digits, it actually corrects the number entered and updates the cell.

I am seeing some very strange results where sometimes the macro works and other times it does not.  Please enter the code below in a blank Excel workbook and try this out.
Private Sub Worksheet_Change(ByVal target As Range)

If target.Cells.Count > 1 Then Exit Sub

If target.Value = "" Then Exit Sub

If Not (IsNumeric(target)) Then
    MsgBox "please enter a number"
    target.Value = ""
    Exit Sub
End If

Call roundit(target, 0.1)

End Sub

Sub roundit(ByVal target As Range, rez As Single)

Dim x As Single

Application.EnableEvents = False

Select Case rez
Case 0.1
    x = Round(target * 10, 0) / 10
    target.NumberFormat = "0.0"
    MsgBox "Rounded value of " & target & " to the nearest " & rez & " is " & x
    target = x
End Select

Application.EnableEvents = True

End Sub

Open in new window

Try entering these test values:

5 - works
5.54 - correctly changes to 5.5
5.45 - appears to work, but the number in the cell is now 5.40000009536743
5.454545 - correctly changes to 5.5
5.656565 - appears to work, but the number in the cell is now 5.69999980926513
6.899 - appears to work, but the number in the cell is now 6.90000009536743
Etc.  I can't find the pattern!

I've got a number of possible rounding values, hence the select case, but for this example I have just provided one.  I've followed the steps in my rounding algorithm and they appear to be working correctly.  It's gotta be a math thing.  Where are these crazy long values coming from, and how do I get this to work correctly?

Appreciate any help!
Nine coins of which three are gold and six are silver in a box. Three coins are selected and placed in bag A. The remaining coins are placed in bag B.
1. Find the probabilities of each possible numbers of gold coins, from 0 to 3, in bag A.

2. on a particular case it is know that one gold coin and two silver cons are in bag A, and that the remaining coins are in bag B. One coin is drawn from a bag selected randomly and put it into another bag. If one coin is then drawn from the last bag, find the probability that it is a gold coin.
Three ordinary dice are thrown. If the first throw results in just two dice showing the same number, then the die with different number is thrown again. If all numbers are different in the first throw, then all are thrown again. If all numbers are different in the first throw, then all are thrown again. Find the probability that

1. all numbers are the same
2. all numbers are different in a complete turn.

Proper AWG for low voltage application.

I want to run some wire for a low voltage lighting.  The transformer supply will be about 6 -8 feet from the LED lights.  Transformer max output is rated at 36 watts.
36w / 12v = 3Amps.  (max)

Question: What would be safe wire gage to use ?  Was considering using 16AWG lamp cord ?   Most of the documentation and/or charts that I can find online shows 16AWG would be sufficient.  See Attached.
Do I need a water-water heat exchanger to run a shower off an Antminer S9-Aqua?

My hovel is currently heated by several crypto-miners but they all blow hot air out and do not provide hot water. If I get a water-cooled mining rig can I connect it directly to my hot water tank or do I need a heat exchanger?

I live in a hard water area. there is a lot of chalk in the tap water which makes it taste nice but tends to clog the pipes.
Please help me to identify the correct type or find a replacement alternative to the broken mini push button used in GPS Prestigio Geovision 5055 as seen in the photos from attached pdf file.