Melody

921 Questions
34316 Answers

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Mathigon website

I just discovered a site called mathigon

https://mathigon.org/dashboard
lire plus ..

Melody 2 avr. 2022

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Reporting problems.

There are a number of people having problems at the moment.
If you lodge an error can you please give all relevant information that you can think of.
Where you are in the world - the city or the country - is often very important information. lire plus ..

Melody 16 mars 2022

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How to make an empty rectangle in Latex

I just worked out how to make an empty box of various horizonal size easily in LaTex.
This is not a recommended method, but other methods that I have tried here have not worked.
This coding is really simple. Just put letters inside lire plus ..

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Melody 15 mars 2022

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HAPPY ANNIVERSARY CHRIS! (CPhill)

I just realized that you became a member here exactly 8 years ago today!

It has been great to have you here all that time

Hors sujet

Melody 13 mars 2022

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WELCOME BACK CPHILL !

Melody 11 févr. 2022

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Very interesting question. No high level maths required.

This question was posted a couple of days ago.
https://web2.0calc.com/questions/geometry_73561

I think it is really interesting. It looks much more difficult than it really needs to be. lire plus ..

Melody 1 févr. 2022

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Members have a better experience. Their questions get more attention.

Almost everyone is posting as a guest.
If you post as a member your questions will have a far greater chance of a timely and helpful response.
If you are a genuine learner and interact with us, you will become known and answerers will do lire plus ..

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Melody 9 janv. 2022

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HAPPY BIRTHDAY CHRIS!

Melody 20 déc. 2021

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Some guidelines for question askers.

Please note:
1) Ask only one question per post.
2) When asking a question talk about what you have tried for yourself. Then people will take you more seriously and will be more able and willing to help.
3) If you get an answer lire plus ..

Hors sujet

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Melody 4 nov. 2021

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Remeniscing - a little historical humour.

I just found this old post that some of you, who have been around for a while, might find amusing.

https://web2.0calc.com/questions/look-at-the-new-leader-board

Hors sujet

Melody 29 oct. 2021

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what is the square root of 7

It is an irrational number and it is already as simple as it can be.

You can estimate it's numerical value using your calculator.

Melody28 oct. 2013

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what is the square root of -400

If you don't know about imaginary numbers then there is no answeer, you cannot find the square root of a negative number.

If you do know a little about imaginary numbers the you will know that i=sqr(-1)
so
sqr(-400) = sqr(400) * Sqr(-1)

= 20i

Melody28 oct. 2013

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how to simplify sinx+cosx
or 4cosx +3sinx

You can't

Melody28 oct. 2013

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Peter's answer is perfect but for some of you, who are less comfortable with algebra you may like to look at it this way.

Firstly, no matter how many windows there are in the building, the answer will be the same.
Just to make it easier I'm going to say there are 150 windows in the buiding

worker one takes 15 hours to wash them all so he must be washing 150/15 = 10 windows per hour
worker two takes 10 hours to wash them all so he must be washing 150/10 = 15 windows per hour

Together they will wash 10+15 = 25 windows per hour

150 windows at 25 windows per hour is 6 hours.

Melody28 oct. 2013

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The mathematical model I got was 10(1+2)^24
The question asked was How much money will you have after 4 weeks?

sorry Regan, your question does not make sense, and I am also sorry that you don't like maths too. I think that maths is fascinating. Never mind, we can't all like everything.

Maybe your question was meant to be something like

10(1+2%)^n ? where n was in weeks and 10 is how many there were to start with ?

Melody28 oct. 2013

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If there is $1.00 to share with 2 people, how much will it be?

I get 98c and the other 2 get 1c each

Melody28 oct. 2013

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If a sales clerk receives a 8% commision on all sales,find the commission the clerk receives on the sales of a computer system costing $1,699.97

=8% of $1699.97

= 8/100 * 1699.97

Melody27 oct. 2013

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The cost price of a car is 450 Naira and the selling price is 504 Naira. What is the percentage gain?

gain=504-450= 54

percentage gain = gain / original price * 100%

Melody27 oct. 2013

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http://www.mhhe.com/math/precalc/barnettpc5/graphics/barnett05pcfg/ch07/others/bpc5_ch07-06.pdf (Page 557)

Thanks peter,
Your explanation helped a lot.
I got more of an explanation from the above web page and after looking at the diagram on page 557 and adding it to knowledge I already have I understood exactly.

I would like to see a proof of why e ^(i*theta) = cos(theta) + i*sin(theta)
The artical says that this relationship is shown/proved in a more advance area.

Thanks again,

Hi Baummann
Sorry I hijacked your post. Do you understand now?

Melody27 oct. 2013

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Hi Peter,
I was looking at this question when your answer was posted
I also got the first 3 lines of your working but I don't see how e^(24.52585093i) becomes e^(5.676295008i)
I'd also really like to understand the next line as well.
I would be really grateful if you could explain this.
thanks.

10^(5 + 10i) * (5e^(3i))^0.5
10^5 * 10^(10i) * 5^0.5 * e^(1.5i)
223606.7977 * e^(24.52585093i)
223606.7977 * e^(5.676295008i)
223606.7977 * cos(5.676295008)+223606.7977 * sin(5.676295008) i
183676.3253-127526.4973i

Melody27 oct. 2013