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Math / Science

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Exactly that
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Ok, so I am a beginner to trigonometry, and how do you convert a decimal to a degree? I dunno if i worded it dorrect, but a website said tan 0.5 is 26.6. I still duno if thsts correct, but if it is, someone explain in good detail on how they got 26.6 degrees? I know how to invert, tan,sin,and cos, coordinates,cortesian coordinates, perpendicular lines, right angles, reciprocals (correct me if im wrong, fraction interchanging?) So can someone simply explain how they got 26.6? Thanks.
hi to all,

I have a vector in Matlab which contains samples acquired at 10Hz from an accelerometer mounted on a frame's vehicle.
This vector contains the acceleration values along the Z-axis.
The acquisition time is 103 seconds.

I would like to plot the frequency values in Hz since I'm trying to study the terrain frequency response.

I tried to use the fft function available in Matlab, but I do not know how to proceed.
Can you help me, please?

These are the values contained in my vector:

ans =
        1024           1
vibration =

Open in new window

Is it related to the fact that we do not know any rule regarding their distribution to date?

For example we have generated lists of several billion Consecutive Prime Numbers and it turns out that there does not seem to be a rule regarding the gaps between each number or at least not on an acceptable human scale .. ... .....

There does not seem to be a rule regarding the gaps between each number …

Here you can download 2 of our small generated lists, the first one containing the first 10'000'000 and the second one containing the first 100'000'000 consecutive Prime Numbers all listed in the correct order with their exact positions, as well as the gap between each number.

Are there any available very long and detailled lists of Large Prime Numbers that allow for larger-scale analysis of the gaps between numbers ?

Or is there a mathematical rule to quantify those number gap or to know their emerging sequence?

Thank you in advance for your answers .. ... .....


I am doing a fitness trainer course alongside my computing and I am confused about the terms used to rotate the hip. The images on Google images also seem to be conflicting

Imagine the knee is bent and lifted up I thought lateral rotation was moving the hip away from the midline of the body to the leg makes a 'r' shape with the feumr being the top of the r and medially rotation was turning it back to its starting position.

This page states that external rotation is lateral rotation and it is the rotary movement that is occurring in the vertical axis when the femur moves away from midline, thereby turning the thigh or pelvis outward.1 the hip can rotate externally 45 degrees.


I extrpaolate from that that medial roation is internal rotation. Correct?

However the image I have attached called incorrect internal and external extension seems to suggest the opposite of the website. The second image is what I would have expected to see

Is the first image incorrect or have I misunderstood as there are so many different sites and pictures it can get confusing. But the second image is intuitive which does make it feel correct. The first image could be a labeling error. I hope so :)

Many thanks in advance
Hello everybody,

It seems generally admitted that there are no negative prime numbers.

What are the rules that can affirm this?

Thanks in advance and happy new year to all.

Best regards,
I am looking for a single mathematical formula that takes in elevation, temperature, humidity and barometric pressure, and gives the speed of sound as an answer. I have found many simplified formulae which use only one variable to give an approximate answer but can't find one that provides a more accurate answer. I realize this may be out of the scope of experts exchange, but thought it can't help to ask.
I am drawing rectangle using 4 points. User should resize rectangle by mouse drag one of rectangle points. So program should  appropriately calculate two neighboring points of the rectangle while the diagonally opposed point is stationary.

Calculating is simple if rectangle is not rotated, but how to calculate points if it is rotated.... for example 30 degrees ?
It is mathematical and program problem and I am a little short how to do it in C++.
twitter sentiment analysis using Matlab   , kindly tell me whenever i import MaxentTagger class , i generate error that *. is must fot import statement..

Even i put *. but still MaxentTagger methods are not imoported in my program.....    

function result = PosTaggerM(str)
      import java.io.*;
      import edu.stanford.nlp.tagger.maxent.MaxentTagger.*;

      % This initialization is expensive.
        % It is better to create the tagger once and then reuse it.
      tagger = MaxentTagger('C:/Program Files/MATLAB/R2017a/bin/english-left3words-distsim.tagger');
      result = java.util.ArrayList();
      sentences = MaxentTagger.tokenizeText(StringReader(str));
      for ii = 1:size(sentences)
            tSentence = tagger.tagSentence(sentences.get(ii-1));

ERROR GENERATED on RUN     Undefined function or variable 'MaxentTagger'.

Error in PosTaggerM (line 40)
      tagger = MaxentTagger('C:/Program Files/MATLAB/R2017a/bin/english-left3words-distsim.tagger');
I watch and have looked at information to get me  as far as I am now all I need before I can run is to target it I know its com  but have no I idea on the prefix
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I got the positive number multiplication right and I can kinda do negative numbers . but I cant do both at the same time
my try code
        STA A
        STA B
        LDA A
        BRZ END
        LDA B
        BRZ END
        LDA NUM
        SUB B
        BRP CHANGE
        SUB B
        STA B
        LDA NUM
        SUB A
        STA A
        BRZ END
        SUB ONE
        STA B
        LDA P
        ADD A
        STA P
        BRA LOOP
        SUB P
        STA P
A       DAT
B       DAT
P       DAT 0
ONE     DAT 1
NUM     DAT 0
This could be an easy question and in fact, this is simple. But just wondering what's the proper algorithm for lucky draw chances?

Let's say in every new deposit amount of X get a no of chances of Y. Providing X = $1000, Y = 1

If there's a customer A credited $10000, he got 10 chances in this month.
If there's a customer B credited $2000, he got 2 chances in this month.
If there's a customer C credited $100, he got 0 chances in this month.
If there's a customer D credited $3500, he got 3 chances in this month.

By end of this month, how do I use a proper algorithm to pick a lucky draw winner? That's to pick a winner among this 15 chances.

One of the approaches is to create multiple chances in a temp table, and then random a position to pick the winner. But my question is what if the total no of chances is a very big number? Will the process of populating this temp table become slow?

Thank you.
calculate the disk capacity transfer rate
given that no. of recording=10,no. of tracks per surface=256,no. of sector per track=32,no. of bytes per sector=128,disk rotation speed=2400 rpm
I will be given a set of X/Y points and their corresponding Z values. Z = f(X, Y), but I do not know the function f. The points will be clustered together and I don't expect pathological conditions. The local maximums and minimums will have extra sample points to help make the interpolation better. The goal is to come up with a smooth surface that represents the function f as close as possible.

The analyst providing me with the set of points of known XYZ points will also give me an XY rectangular grid; and at all the intersection points of horizontal and vertical lines, I need to provide a z-value.

One thought I had was to consider a point and look at 4 quadrants, and take the closest point in each quadrant, and using those 4 points or more to try to interpolate. Prefer to be able to use a curved surface to get the results rather than linear planes. One rule is that the final results will match the given XYZ points . The given points are known as anchor points or knots.

I am just looking for something functional. I am not interested in speed.

 I am not allowed to use binaries, so I will have to build from source code in Linux or Windows.

Thanks in advance.
In a previous question we're shopping for an ingredient which comes in standard pack sizes of either 100g, 250g or 500g, having prices $0.40, $0.75 and $1.00 respectively.


PackSize = {100; 250; 500}
PackPrice = {0.40; 0.75; 1.00}

QuantityNeeded = {0.... up in steps of GCD(PackSize)... MaxQuantity }

GCD = greatest common divisor, eg GCD({100; 250; 500}) = 50

We only need to define a table with intervals in these steps as in between there won't be any change in the cost. I think this logic is right, please correct me if wrong.

We then define f_mincost(QuantityNeeded ) as the set of packs that meets the QuantityNeeded at minimum cost, eg:

f_mincost(1050) gives 1 x 100g + 2 x 500g at a total cost of $2.40

This problem is solved in the previous question by using dynamic programming to create a lookup table of values:

a) Quantity needed, eg 1050
b) Minimum cost, eg $2.40
c) Pack selection, eg 100, 500, 500

1. What MaxQuantity do we need to tabulate upto before the pattern is repeating
    ie MaxQuantity = some function of Packsize
2. How can we define f_mincost(QuantityNeeded) as a function of this repeating pattern
   eg what is f_mincost(6400) as a function of f_mincost(some value <= MaxQuantity)

This is is probably straightforward but after the previous question my head has been frazzled!

Thanks again
Write a function called my_gcd() that takes parameters a and b and returns their greatest common divisor. Create your own implementation of the algorithm and test your code by comparing the output of your function to Python's gcd() function from math package.Test the code with the following inputs: (39, 91), (20, 30) and (40,40). Explain the logic of your function.
1. Write the pseudocode and draw the flowchart for a hotel program to determine the cost a customer has to pay for a stay based on the following pricing policy of the choice of room:
>>>Room for 1 to 2 people: RM85
>>>Room for 3 to 4 people: RM90
>>>Room for 5 to 6 people: RM120
>>>Room for > 6 people, RM125 plus charge for additional people at RM25 per person

If the customer has a membership card, there is a 20% discount. If the customer wants to pay using credit card, there is a 15% discount. A customer cannot receive both discounts. If the customer wants to pay using credit card and has a membership card, the highest discount rate will be given.

Answer these questions before you start solving the problem.
What is the output?
→Cost of customer has to pay for a stay
How many input(s) is/are needed?
What is/are the input(s)?
→number of people, number of days, payment type,
What is the process (equation) to find the output?                                                                                                                    
→cost = number of days * 85
→cost = number of days * 90
→cost = number of days * 120
→additional people = number of people - 6
→cost = number of days * [125 + 25 (additional people)]
→membership card =  cost * 80/100
→credit card = cost * 85/100
How many different calculation(s) is/are needed?
What structure need to be used to select which is the correct calculation to use? Repetition or decision? →decision…
It is for a science project we just don't have any weighing scales to test it ourselves
How much more will the cost be for a wager on V5 compared to V4 when adjusting for difference in probability, price per unit and track's deduction?:

For V5 (a type of wagering on harness racing where you should pick the winner in 5 races), the probability to pick the winners in the five races is 12 times more difficult compared to for V4 (1/248832 divided with 1/20736; (12x12x12x12x12)/(12x12x12x12)), which means you need to spend 12 times more units on V5 to achieve the same probability. However, this should be adjusted first for price per unit, which for V4 is 2 SEK and for V5 is 1 SEK, so the adjustment becomes 12 x 0.5 = 6.

The final adjustment is for the racing track's deduction, which for V4 is 25 % and for V5 is 35 %.

Is this correct?:

6 + (0.1/0.25) = 6.4

Which means in order to compensate for lower probability in V5 compared to V4, and for difference in price per unit (V4: 2 SEK; V5 1 SEK) and difference in track's deduction (V4: 25 %; V5 35 %), I need to spend 6.4 times more units/money on V5 compared to V4 so that I in the end have the same probability to win on my wager on both V4 and V5, provided that the payouts on both the wagers are the same.

Or do I get it wrong? Is it that the payout on V5 needs to be 6.4 times higher than on V4 in order to compensate for the difference in probability, price per unit and track's deduction?
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I am trying to rotate an object and get the following error message: 1119:access of possibly undefined property Math through a reference with a static type class. Thank you for your help

 here is the code

import flash.events.MouseEvent;

stage.addEventListener(MouseEvent.MOUSE_MOVE, FollowMouse);
function FollowMouse(event:MouseEvent):void
      var SideY:Number = mouseY-circle.Y;
      var SideX:Number = mouseY-circle.X;
      var Rad:Number = Math.atan2(SideY,SideX);
      var Deg:Number = Rad * 180/Math.PI;
      circle.rotation = Deg;
The following problem refers to strings in A, B, ..., Z.

How many four-letter strings are there that begin with O ?
I heard gastritis and heartburn can be solved by ingesting alkaline substances.
Alkaline plants supposedly containing alkaline substances can be ingested to lower the pH value in the stomach due to stomach acid.
I'm trying to extract alkaline substances from plants using simple boiling extraction.
Thus, I tried to extract alkaline substances from a alkaline plant, dandelion, in ethanol and ethyl acetate solvent for 10~15 minutes.
The solution was filtered with carbon black for decolourization, but it didn't show alkaline colour with universal indicator.

So... I've got some questions to ask

1. Is dandelion alkaline?
2. If it's alkaline, is it possible to extract alakline substances or alkaloids from the plant?
3. If dandelion is not alkaline enough, then could there be any othe ralternative plant or food that can be extracted alkaline substances?
4. Is alkaloid alkaline?
5. What are the alkaline substances coming from?
6. If the simple boiling extraction doesn't work , is there any other ways that I can extract alkaline substances from the plants?

Could you explain in high school level.
I hope this forum can also help regarding electricity science.
Need to purchase a few single cells of lipo and ni-mh battery types >> high drain >> for airsoft purpuse, and rc!

1. Would like to get anykind information to get them from any Europe dealers, wholesalers,distributors, etc?
2. Or, name of a few manufacturers companies?

Thanks in advance...
I wish to extract info from a land registry file - see info on this link.


I have a UK land registry .gml file downloaded from their site


I have installed QGIS and have managed using the menu item FILE / IMPORT VECOR DATA / COMMON IMPORT FORMATS browsed to the .gml file and opened it but all I see is View1 ( attached ). I can zoom to produce View2 & 3 ( also attached )  but I can't see how I can reveal the Polygons referred to by the Land Registry.
Due respect sir,
The we questions is that

(A×B.C)(a×b.c)=|A.a.      A.b.      A.c.  |
                           |B.a.        B.b.     B.c.  |
                           |C.a.       C.b.      C.c.   |

Sir as soon as possible plz send the solution my mail

                   Thank you
                  Your student

Math / Science

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